feat(auto): page local-music folders instead of truncating at 50 [size:exception]

Folders over the 50-item cap now show a "Mas..." item that reveals
the next page on tap, instead of silently dropping the rest. Paging
slices the cheap raw list before building any MediaItem, so items
beyond the requested page are never resolved (art, title) -- proven
by a call-count test. Also swaps the raw SAF content:// URI shown in
settings for a parsed, human-readable folder name with a localized
fallback across all 13 locales.

servicio_audio.dart is untouched; this stays entirely within the
local-music tree/dispatch layer.

openspec/changes/android-auto-local-music-paging/apply-progress.md

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+# Apply Progress: android-auto-local-music-paging
+
+Status: DONE — all 18 tasks across 8 phases completed in a single apply batch
+(first and only batch), delivered as one PR with `size:exception` per the
+resolved delivery strategy.
+
+## Tasks Completed: 18 / 18
+
+- Phase 1 (Paging Primitives): 1.1-1.4 — done
+- Phase 2 (Paged Media-ID Scheme): 2.1-2.2 — done
+- Phase 3 (Paged `itemsLocales` + "Más…" Item): 3.1-3.5 — done
+- Phase 4 (Wire Paged ID into `hijosMusicaLocal`): 4.1-4.2 — done
+- Phase 5 (Friendly Folder Name): 5.1-5.2 — done
+- Phase 6 (Localization): 6.1 — done (13/13 locales)
+- Phase 7 (Settings UI Wiring): 7.1 — done (implementation); widget test
+  written but not executable in this sandbox (see Deviations)
+- Phase 8 (Regression / Manual Follow-Up): 8.1 — done (verified via targeted
+  test re-runs); 8.2 — deviated as originally documented (manual follow-up,
+  unchanged from tasks.md's own note)
+
+## TDD Discipline
+
+Strict TDD mode was active. RED was confirmed via actual compile failures
+(missing symbols / signature mismatches) before each GREEN implementation
+step for:
+- `paginaDe<T>` / `hayPaginaSiguiente` (Phase 1) — implemented alongside the
+  first test batch write (single edit pass covered both primitives), tests
+  then run and passed; no separate RED capture for this pair specifically
+  since both are trivial one-line pure functions added in the same edit as
+  their tests were authored.
+- `esCarpetaLocalPaginadaMediaId` / `paginaCarpetaLocalDesde` / paged
+  `itemsLocales` / paged `hijosMusicaLocal` (Phases 2-4) — RED confirmed via
+  a full `flutter test test/servicios/navegacion_auto_test.dart` run showing
+  ~20 compile errors (`Method not found`, `No named parameter`) before the
+  GREEN implementation, then a second run confirming 84/84 passing.
+- `nombreCarpetaDesdeUri` (Phase 5) — RED confirmed via
+  `flutter test test/servicios/musica_local_auto_test.dart` showing 5
+  `Method not found: 'nombreCarpetaDesdeUri'` compile errors before GREEN,
+  then 10/10 passing after.
+- Settings UI wiring (Phase 7) — RED attempted via
+  `flutter test test/pantallas/pantalla_ajustes_test.dart`, but this
+  surfaced a PRE-EXISTING environment blocker unrelated to this change (see
+  Deviations #1). The implementation was completed to spec regardless.
+
+## Files Changed
+
+Production code:
+- `lib/servicios/navegacion_auto.dart` (+119/-lines within diff) — added
+  top-level `paginaDe<T>`, `hayPaginaSiguiente`; added
+  `_prefijoCarpetaLocalPaginada`, `esCarpetaLocalPaginadaMediaId`,
+  `paginaCarpetaLocalDesde`, `_tituloMasLocal`, `_itemMasLocal`; extended
+  `itemsLocales` signature (`documentIdPadre`, `pagina`, `tamano`,
+  `@visibleForTesting construirItem`) with slice-then-map ordering (ADR-3);
+  added paged branch to `hijosMusicaLocal`.
+- `lib/servicios/musica_local_auto.dart` (+47 lines) — added pure
+  `nombreCarpetaDesdeUri(String treeUri, {required String nombreGenerico})`.
+  Signature note: takes the localized fallback text as a plain `String`
+  parameter rather than a `BuildContext`, so the function stays pure and
+  unit-testable without a widget tree (mirrors the
+  `_formatearDuracion(AppLocalizations l10n, ...)` precedent in
+  `pantalla_reproductor.dart`, minus the generated-class coupling). This is
+  a refinement of tasks.md's terse "`nombreCarpetaDesdeUri(String) -> String`"
+  description, the same kind of abbreviation gap task 3.4 already had for
+  `itemsLocales`'s full signature.
+- `lib/pantallas/pantalla_ajustes.dart` (+5/-2 lines) — `_SeccionMusicaLocal`
+  subtitle now renders
+  `nombreCarpetaDesdeUri(carpeta, nombreGenerico: l10n.localMusicFolderGenericName)`
+  instead of the raw persisted URI; the unconfigured branch is unchanged
+  (`l10n.localMusicFolderNotConfigured`).
+- `lib/l10n/app_{ar,bn,de,en,es,fr,hi,id,it,ja,pt,ru,zh}.arb` (13 files,
+  +1 key each) — added `localMusicFolderGenericName`, matching each locale's
+  existing `localMusicFolder*`/`localMusicChoosePath` register. No "Más…"
+  arb key added anywhere (ADR-5 — that label is hardcoded Spanish car-tree
+  text, matching every other car-tree label in `navegacion_auto.dart`).
+
+Tests:
+- `test/servicios/navegacion_auto_test.dart` (+453 lines) — new groups:
+  `paginaDe`, `hayPaginaSiguiente`,
+  `esCarpetaLocalPaginadaMediaId / paginaCarpetaLocalDesde`; rewrote/extended
+  `ConstructorArbolAuto.itemsLocales` group (call-count invariant, exact-50
+  boundary, 51-100 two-step, 100+ chained 3+ pages, "Más…" item shape/round
+  -trip, root paging, stale-page-beyond-range, plus all 8 pre-existing call
+  sites updated to pass `documentIdPadre`); extended `hijosMusicaLocal`
+  group with 4 new paged-branch tests.
+- `test/servicios/musica_local_auto_test.dart` (+84 lines) — new
+  `nombreCarpetaDesdeUri` group: internal storage, SD card, nested folder,
+  storage-root empty-tail fallback, unparseable-URI fallback, never-raw
+  -URI/never-empty invariant.
+- `test/pantallas/pantalla_ajustes_test.dart` (+57 lines) — new group
+  `_SeccionMusicaLocal — friendly folder name (Phase 7)`: configured folder
+  shows the derived friendly name (never the raw `content://` URI);
+  unconfigured folder keeps the existing "not configured" message. Written
+  to spec but NOT executable in this sandbox (see Deviations #1).
+
+## Test Results (independently re-confirmed)
+
+- `flutter test test/servicios/navegacion_auto_test.dart test/servicios/musica_local_auto_test.dart --concurrency=1 --timeout=60s`
+  → **94 / 94 passing** (84 tests in `navegacion_auto_test.dart` + 10 tests
+  in `musica_local_auto_test.dart`) — corrected during verify, the figure
+  above (95/95, 85+10) originally reported here was a counting error.
+- `test/pantallas/pantalla_ajustes_test.dart` — NOT run to completion; fails
+  to COMPILE in this sandbox for reasons that predate this change entirely
+  (see Deviations #1). The 2 new tests in this file are structurally
+  complete and should pass once `flutter gen-l10n` is run as part of the
+  normal manual follow-up (task 8.2), which already covers regenerating
+  l10n artifacts.
+
+## Diff Size
+
+`git diff --stat`: 19 files changed, 764 insertions(+), 40 deletions(-)
+(≈804 changed lines). This exceeds the tasks.md forecast of ~480-600 lines,
+mainly because task 3.5's "mechanical" call-site update also required
+rewriting one pre-existing assertion (the 60-item cap test) into two new
+boundary tests reflecting the spec's cap→paging behavior change, plus the
+call-count-invariant test's verbosity (4 assertions × explicit spy
+wiring). Delivered as a single PR with `size:exception`, as directed.
+
+## Deviations
+
+1. **`pantalla_ajustes_test.dart` cannot compile in this sandbox —
+   pre-existing, not introduced by this change.** The tracked
+   `lib/l10n/gen/app_localizations.dart` is stale: it predates even the
+   PARENT local-music change and is missing `localMusicFolderNotConfigured`,
+   `localMusicSectionTitle`, `localMusicFolderTitle`, etc. — getters the
+   file already referenced BEFORE this apply pass touched anything.
+   Confirmed by running the targeted test file and observing the compiler
+   errors point exclusively at pre-existing lines (320-383) before any new
+   code from this change is even reached. Regenerating the l10n artifacts
+   requires `flutter gen-l10n`, which is documented to hang in this
+   environment and was explicitly out of scope for this apply run (per
+   task 8.2, already flagged as a manual follow-up in the original
+   tasks.md). The new `localMusicFolderGenericName` getter this change adds
+   will appear automatically once that regeneration happens — no code
+   change is needed on top of what's here.
+2. **The pre-existing 60-item `itemsLocales` cap test was rewritten, not
+   just signature-patched**, as part of task 3.5. This was flagged in
+   tasks.md as "mechanical, no behavior change" for the 8 call sites in
+   aggregate, but this ONE specific test's assertion (exactly 50 items,
+   full stop) is incompatible with the spec's Modified Requirement ("Local
+   Music Folder Item Cap and Paging" — cap-and-truncate replaced by
+   cap-and-page). It was split into two new tests that assert the correct
+   NEW behavior (exactly 50 items → no "Más…"; 51-100 items → 50 + "Más…"
+   then the remainder). This is an intentional, spec-mandated behavior
+   change, not a regression.
+
+## Risks Carried Forward
+
+- Re-enumerating the folder per "Más…" tap repeats one SAF query per ADR-2
+  (accepted, documented, out of scope to change here).
+- Pure-Dart friendly-name derivation is brittle for exotic SAF providers
+  (accepted per ADR-4 — degrades to the generic label, never a crash/blank
+  /raw-URI).
+- `flutter analyze` / `flutter gen-l10n` / full `flutter test` were not run
+  in this session (environment constraint) — task 8.2's original deviation
+  note stands, now also explains Deviation #1 above.

openspec/changes/android-auto-local-music-paging/design.md

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+# Design: Android Auto Local Music — On-Demand Paging + Friendly Folder Name
+
+Executor: sdd-design. Reads: `proposal.md` (this change), base spec
+`openspec/specs/android-auto-media/spec.md`, live code
+(`navegacion_auto.dart`, `servicio_audio.dart`, `musica_local_auto.dart`,
+`pantalla_ajustes.dart`, `MainActivity.kt`).
+
+## 1. Architecture Approach
+
+**Pure-Dart, additive on the existing browse seams — zero new state, zero
+native surface.** The Phase 1 local-music tree is a *stateless, cold-start-safe,
+never-throws* pipeline: `getChildren` → `hijosMusicaLocal` → `fuente.hijos()`
+(one SAF level) → `ConstructorArbolAuto.itemsLocales` (pure mapping). This change
+extends that pipeline WITHOUT introducing the pipeline's first piece of mutable
+state. Paging is expressed as three pure, testable transforms:
+
+1. a generic slice function (`paginaDe<T>`) that operates on the **cheap**
+   `NodoLocal` DTO list BEFORE any `MediaItem` is built;
+2. a "next page exists" predicate (`hayPaginaSiguiente`);
+3. a synthetic browsable "Más…" trailing item whose media-id round-trips the
+   `(documentId, nextPage)` pair back through `getChildren`.
+
+The friendly folder name is a fourth pure transform (`nombreCarpetaDesdeUri`) on
+the persisted SAF URI string, used only by the phone settings UI.
+
+Nothing here needs a `MethodChannel`, a package, or a widget tree. Everything is
+unit-testable in isolation — required by the active Strict TDD mode.
+
+## 2. Component & Data-Flow Map
+
+```
+CAR browse "Música Local" folder tap
+  ServicioAudio.getChildren(parentMediaId)                 [servicio_audio.dart]
+    └─ hijosMusicaLocal(parentMediaId, fuente)             [navegacion_auto.dart]
+         resolves parentMediaId into (documentId, pagina):
+           idMusicaLocal            -> ('',      0)
+           carpeta_local:<docId>    -> (<docId>, 0)
+           carpeta_local_pag:<n>:<docId> -> (<docId>, n)   ← NEW branch
+         └─ fuente.hijos(documentId)   -> List<NodoLocal>  [musica_local_auto.dart]
+              (native listAudioChildren returns the WHOLE level; unchanged)
+         └─ constructor.itemsLocales(nodos,
+                 documentIdPadre: documentId, pagina: pagina)
+              1. sort full NodoLocal list (cheap)          ← O(n log n), no MediaItem
+              2. paginaDe(ordenados, pagina, 50)           ← slice CHEAP list first
+              3. slice.map(_itemLocal)                     ← build ≤50 MediaItems ONLY
+              4. if hayPaginaSiguiente(...) append "Más…"   ← carpeta_local_pag:<n+1>:<docId>
+
+PHONE settings "current folder" row                        [pantalla_ajustes.dart]
+  _carpetaActual (raw content:// tree URI)
+    └─ nombreCarpetaDesdeUri(uri) -> friendly name         [musica_local_auto.dart, NEW]
+```
+
+Every arrow is synchronous pure Dart except `fuente.hijos()` (the existing native
+SAF query) — unchanged from Phase 1.
+
+## 3. Load-Bearing Decisions (ADRs)
+
+### ADR-1 — Paged media-id scheme: `carpeta_local_pag:<page>:<docId>`
+
+**Decision.** The "Más…" item's id is
+`carpeta_local_pag:<nextPage>:<rawDocumentId>`, where `<nextPage>` is the
+zero-based index of the page to LOAD when tapped, and `<rawDocumentId>` is the
+parent folder's SAF documentId **verbatim** (may itself contain `:` and `/`).
+
+**Parsing.** Strip the `carpeta_local_pag:` prefix by length, then split on the
+**first** `:` only: everything left of it is the page integer (never contains a
+colon), everything right of it — including any further colons/slashes — is the
+raw documentId. Root paging is expressible: the root docId is `''`, so root
+page 1 is `carpeta_local_pag:1:` (empty tail).
+
+**Collision proof** vs the 5 existing prefixes (`emisora:`, `grupo:`,
+`eq_preset:`, `carpeta_local:`, `pista:`) and bare folder ids
+(`favoritos`/`todas`/`mis_emisoras`/`ecualizador`/`musica_local`):
+- The only near-neighbor is `carpeta_local:`. `carpeta_local_pag:...` does NOT
+  start with `carpeta_local:` — at index 13 the paged token has `_`, the plain
+  prefix has `:`. Symmetric­ally, a plain `carpeta_local:<docId>` never starts
+  with `carpeta_local_pag:` for the same reason. The two predicates are mutually
+  exclusive; routing order between them is irrelevant to correctness (paged is
+  checked first only for readability).
+- New predicate `esCarpetaLocalPaginadaMediaId(id) => id.startsWith('carpeta_local_pag:')`
+  and parser `paginaCarpetaLocalDesde(id) -> (String docId, int pagina)` live
+  next to the existing `esCarpetaLocalMediaId` / `idCarpetaLocalDesde` helpers,
+  mirroring their "strip by length, survive raw `:`/`/`" convention.
+
+**Encoding the page directly in the id (chosen) vs. an opaque page token.**
+Encoding the page number literally keeps the whole pipeline stateless — the id
+IS the cursor. No server-side page registry, no session token to expire. This is
+the established `MediaBrowserService` "load more via synthetic item" workaround
+and is fully deterministic.
+
+### ADR-2 — Re-query the folder on every "Más…" tap; do NOT cache
+
+**Decision.** Each "Más…" tap re-invokes `fuente.hijos(documentId)` (one native
+SAF query returning the full level), re-sorts deterministically, and slices to
+the requested page. **No in-memory cache of raw entries between taps.**
+
+**Why re-query wins over a session cache.**
+1. **Preserves the single most valuable property of this layer: statelessness.**
+   The browse pipeline is currently pure and cold-start-safe. A cache would be
+   the FIRST mutable field in it, dragging in invalidation, staleness, clear-on-
+   revoke, and thread-safety concerns — disproportionate to the benefit.
+2. **Determinism already guarantees stable page boundaries.** The sort
+   (`a.nombre.compareTo(b.nombre)`) makes page N identical across re-queries as
+   long as the folder is unchanged, so re-slicing is correct without a cache.
+3. **Freshness.** Re-query reflects on-disk changes between taps; a cache would
+   serve stale entries.
+4. **Cost is user-triggered and off the hot path.** SAF `listAudioChildren` is a
+   single `ContentResolver.query` + cursor walk, fast for realistic folders, and
+   runs only when the driver explicitly taps "Más…" — not on a timer or during
+   playback.
+5. **Matches the proposal's stated intent** ("Nothing is cached between taps →
+   minimal memory") and YAGNI.
+
+**Escape hatch (designed-for, not built).** If real-world profiling ever shows
+pathologically large folders make the re-query sluggish, a session-scoped cache
+of the cheap `List<NodoLocal>` keyed by documentId is a localized, additive
+optimization that slots BEHIND the same pure `paginaDe` seam without changing the
+media-id scheme or the mapping contract. Not in scope now.
+
+### ADR-3 — Memory guarantee: slice the cheap list, THEN map (never map-then-slice)
+
+**Decision.** `itemsLocales` MUST build `MediaItem`s for AT MOST
+`min(tamano, remaining)` entries per call — never one per total-folder-size. This
+is enforced structurally by ordering the operations:
+
+```dart
+List<MediaItem> itemsLocales(
+  List<NodoLocal> nodos, {
+  required String documentIdPadre,
+  int pagina = 0,
+  int tamano = _maxItemsCarpetaLocal,               // 50
+  @visibleForTesting MediaItem Function(NodoLocal)? construirItem,
+}) {
+  final construir = construirItem ?? _itemLocal;     // expensive: art rotation + title
+  final ordenados = [...nodos]..sort((a, b) => a.nombre.compareTo(b.nombre));
+  final pagina0 = paginaDe(ordenados, pagina: pagina, tamano: tamano); // CHEAP slice
+  final items = pagina0.map(construir).toList();      // build ONLY the slice
+  if (hayPaginaSiguiente(ordenados.length, pagina: pagina, tamano: tamano)) {
+    items.add(_itemMasLocal(documentIdPadre, pagina + 1));
+  }
+  return items;
+}
+```
+
+with the generic, reusable, pure helpers:
+
+```dart
+List<T> paginaDe<T>(List<T> items, {required int pagina, required int tamano}) =>
+    items.skip(pagina * tamano).take(tamano).toList();
+
+bool hayPaginaSiguiente(int total, {required int pagina, required int tamano}) =>
+    total > (pagina + 1) * tamano;
+```
+
+**The expensive mapper (`_itemLocal`) is injectable via a `@visibleForTesting`
+parameter** so the memory constraint is an *asserted* architectural invariant,
+not a comment. `@visibleForTesting` is already the codebase idiom
+(`debeReaplicarEcualizador`).
+
+**Testable constraint (must exist in the test suite).** Given a folder of 200
+`NodoLocal`s, `itemsLocales(nodos, documentIdPadre: 'x', pagina: 0, tamano: 50,
+construirItem: countingSpy)` MUST invoke `countingSpy` **exactly 50 times**, and
+`pagina: 3` MUST invoke it exactly `min(50, 200 - 150) = 50` times, and the last
+partial page exactly `remaining` times. A naive `nodos.map(_itemLocal).skip().take()`
+regression would call the spy 200 times and FAIL this test — that is precisely
+the regression this seam catches. `paginaDe` is additionally unit-tested in
+isolation: it returns `NodoLocal`s (a type that carries no art/title), so by
+construction it cannot have built a `MediaItem`.
+
+**Boundary cases** (all covered by tests):
+- 50 items / page 0 → 50 items, NO "Más…" (`50 > 50` is false; nothing dropped).
+- 51 items / page 0 → 50 items + "Más…"(page 1); page 1 → 1 item, no "Más…".
+- 0 items → `[]` (Spec "browsing an empty subfolder returns an empty list").
+- Stale page beyond range (folder shrank between taps) → empty slice, no "Más…",
+  `[]`, no throw.
+
+### ADR-4 — Friendly folder name: pure-Dart URI parse with layered fallback (NO native round-trip)
+
+**Native reality (confirmed by static review of `MainActivity.kt`).**
+`pickMusicFolder` returns `treeUri.toString()` — the raw tree URI, nothing else.
+`listAudioChildren` projects `COLUMN_DISPLAY_NAME` for each **child**, but never
+the picked **root** folder's own name. `hasPersistedPermission` returns a bool.
+**No existing native response carries the root's display name** — reusing one is
+impossible. The only alternatives are (A) pure-Dart URI parsing, or (B) a new
+native method returning `DocumentFile.getName()` of the tree root.
+
+**Decision: (A) pure-Dart `nombreCarpetaDesdeUri(String treeUri) -> String`.**
+Zero native surface, fully unit-testable, appropriate for a cosmetic settings
+label. A native round-trip would add a channel method, untestable (in Dart)
+MainActivity code, and an async/permission failure path — disproportionate.
+
+**Algorithm.**
+1. `Uri.tryParse(treeUri)`; on `null` → generic fallback (step 4).
+2. SAF tree URIs are `content://<authority>/tree/<encoded-documentId>`. Dart's
+   `uri.pathSegments` returns already-percent-decoded segments, so the segment
+   after `tree` is the decoded documentId (e.g. `primary:Music/MyFolder`,
+   `1A2B-3C4D:Music`).
+3. Extract the trailing readable part of that documentId:
+   - if it contains `/`, take everything after the last `/` (`…/MyFolder` →
+     `MyFolder`);
+   - else if it contains `:`, take everything after the last `:`
+     (`primary:Music` → `Music`);
+   - trim. If non-empty → **friendly name**.
+4. **Final fallback** (documentId empty/opaque, e.g. a storage root `primary:`
+   or a cloud provider's `msf:123`): a localized generic label
+   `localMusicFolderGenericName` (see ADR-5). **Never** the raw `content://` URI,
+   **never** empty/blank.
+
+**Fallback text is a localized generic label, NOT the raw URI** (a refinement of
+the proposal, which defaulted to raw-URI fallback). The entire purpose of this
+change is to STOP surfacing the raw URI; showing it in the rare unreadable-
+provider case would defeat the intent. `content://…/tree/msf%3A123` is not
+"readable," so the raw URI is never an acceptable fallback. Trade-off: this adds
+ONE phone-UI l10n key across 13 locales (small, and consistent with the "never
+regress locales" lesson). The zero-l10n alternative — falling back to the decoded
+documentId string — is noted but rejected as still-ugly.
+
+**Provider brittleness (accepted risk).** Internal storage and SD card produce
+readable trailing segments; Downloads/cloud providers may produce opaque ids —
+these degrade cleanly to the generic label, never to a crash or a broken string.
+If field reports later show the generic label appears too often for common
+setups, the native `DocumentFile.getName()` round-trip (option B) is the
+pre-identified fallback, isolated to `nombreCarpetaDesdeUri`'s call site.
+
+### ADR-5 — "Más…" item and locale strategy (OVERTURNS a proposal assumption)
+
+**Finding.** The car browse tree labels in `navegacion_auto.dart` are **hardcoded
+Spanish, not localized**: `'Favoritos'`, `'Todas las emisoras'`, `'Ecualizador'`,
+`'Música Local'`, and the track fallback `_tituloLocalFallback = 'Pista sin
+nombre'` — explicitly documented as "hardcoded Spanish, matching every other
+car-tree label in this file… none of which go through `AppLocalizations`." The
+handler resolves l10n to `Locale('es')` by default for the tree.
+
+**Decision — two DISTINCT strings, two DISTINCT locale strategies:**
+
+1. **Car "Más…" item → hardcoded Spanish constant**, NOT an arb key:
+   ```dart
+   const _tituloMasLocal = 'Más…';
+   ```
+   Adding an arb key for ONLY this item while `'Favoritos'`, `'Música Local'`,
+   and `'Pista sin nombre'` stay hardcoded would be architecturally incoherent.
+   The "Más…" item is a car-tree label and MUST follow the car-tree convention.
+   **This overturns the proposal's scope item** "Update ALL 13 `app_*.arb` files
+   for the 'Más…' label" — that item was written assuming the car label is
+   localized like phone UI, which it is not. **No arb change for "Más…".**
+
+   The "Más…" `MediaItem` is browsable (`playable: false`), list content-style
+   (`_contentStyleLista`), **no `artUri`** (consistent with `_carpeta`, which
+   sets none — the label alone is the affordance):
+   ```dart
+   MediaItem _itemMasLocal(String documentIdPadre, int siguientePagina) => MediaItem(
+     id: '$_prefijoCarpetaLocalPaginada$siguientePagina:$documentIdPadre',
+     title: _tituloMasLocal,
+     playable: false,
+     extras: _contentStyleLista,
+   );
+   ```
+
+2. **Phone settings generic folder-name fallback → NEW arb key
+   `localMusicFolderGenericName`** across ALL 13 locales (`ar,bn,de,en,es,fr,hi,
+   id,it,ja,pt,ru,zh`). This is genuine phone UI, which DOES use
+   `AppLocalizations` (`l10n.localMusicFolderNotConfigured`, etc.). The Phase 1
+   "en/es-only omission" lesson applies here: scope all 13 locales from the
+   start. Key name is non-colliding with the 8 Phase 1 keys
+   (`localMusicSectionTitle`, `localMusicSectionDescription`,
+   `localMusicFolderTitle`, `localMusicFolderNotConfigured`,
+   `localMusicChangePath`, `localMusicChoosePath`, `localMusicFolderUpdated`,
+   `localMusicFolderSaveError`). Suggested value: es `"Carpeta seleccionada"`,
+   en `"Selected folder"`.
+
+**Net l10n scope: ONE new phone-UI key across 13 locales — NOT the car "Más…"
+label.** This is the inverse of what the proposal anticipated and MUST be
+reflected in `sdd-spec` / `sdd-tasks`.
+
+### ADR-6 — Reusable generic paging; radio deliberately untouched
+
+**Decision.** `paginaDe<T>` and `hayPaginaSiguiente` are **generic, top-level,
+pure functions** (type parameter `T`, no `NodoLocal` coupling). Any future folder
+type that needs paging can reuse the slice math directly. This satisfies the
+task's "design for reasonable future reuse" without expanding scope:
+
+- The **reusable** part is the slice arithmetic (`paginaDe`/`hayPaginaSiguiente`)
+  — already radio-ready, but no radio code is touched and no radio path calls it.
+- The **domain-specific** part is the media-id encoding (`carpeta_local_pag:`
+  round-trips a SAF documentId). Radio would need its OWN prefix + its own "Más…"
+  builder if it were ever paged — deliberately NOT created here. Radio-station
+  folders (`hijos`, `_maxItemsPorCarpeta`) keep cap-and-truncate, untouched
+  (proposal "Out of Scope"; Spec "Favorite Group…"/station cap requirements
+  unchanged).
+
+### ADR-7 — `getChildren` needs NO change; `hijosMusicaLocal` absorbs the paged id (scope reduction)
+
+**Decision.** `hijosMusicaLocal` already owns ALL local-music media-id shapes and
+returns `null` only for non-local ids so `getChildren` can fall through. By adding
+the `carpeta_local_pag:` branch INSIDE `hijosMusicaLocal`, `getChildren` in
+`servicio_audio.dart` requires **no edit** — it still calls
+`hijosMusicaLocal(...)` and returns the non-null result. This **reduces** the
+proposal's stated scope (which listed a new `getChildren` branch). Verified safe:
+a `carpeta_local_pag:` id equals neither `browsableRootId`, `idEcualizador`, nor a
+`grupo:` id, so it reaches `hijosMusicaLocal` before any other branch. The Más
+item is non-playable, so `playFromMediaId` is never invoked on it; even if it
+were, it matches none of the `eq_preset:`/`pista:`/`emisora:` prefixes and no-ops.
+`playFromMediaId` therefore also needs no change.
+
+## 4. Integration Points / Affected Files (revised)
+
+| File | Change | Detail |
+|------|--------|--------|
+| `lib/servicios/navegacion_auto.dart` | Modified | Add `paginaDe<T>`, `hayPaginaSiguiente`, `_prefijoCarpetaLocalPaginada`='carpeta_local_pag:', `esCarpetaLocalPaginadaMediaId`, `paginaCarpetaLocalDesde`, `_tituloMasLocal`='Más…', `_itemMasLocal`; extend `itemsLocales` signature (`documentIdPadre`, `pagina`, `tamano`, `@visibleForTesting construirItem`) with slice-then-map; add paged branch to `hijosMusicaLocal` |
+| `lib/servicios/musica_local_auto.dart` | Modified | Add pure `nombreCarpetaDesdeUri(String) -> String` |
+| `lib/pantallas/pantalla_ajustes.dart` | Modified | `_SeccionMusicaLocal` subtitle (~line 361) renders `nombreCarpetaDesdeUri(carpeta)` instead of raw `carpeta`; generic fallback via `l10n.localMusicFolderGenericName` |
+| `lib/l10n/app_{ar,bn,de,en,es,fr,hi,id,it,ja,pt,ru,zh}.arb` | Modified | ONE new key `localMusicFolderGenericName` (phone UI). NOT a "Más…" key. |
+| `lib/servicios/servicio_audio.dart` | **Unchanged** | ADR-7: `hijosMusicaLocal` absorbs the paged id; `getChildren`/`playFromMediaId` untouched |
+| `MainActivity.kt` / `pubspec.yaml` | Unchanged | No native / dependency change |
+
+## 5. Overturned Proposal Assumptions (flag for sdd-spec / sdd-tasks)
+
+1. **l10n direction inverted (ADR-5).** Proposal: add the "Más…" label to 13 arb
+   files. Design: "Más…" is a HARDCODED-Spanish car-tree label (matching all
+   existing car-tree strings) — NO arb key. The ONLY new arb key is the phone-UI
+   friendly-name fallback `localMusicFolderGenericName` (13 locales). This does
+   not weaken the "never regress locales" guard — it retargets it to the correct
+   string.
+2. **`servicio_audio.dart` NOT modified (ADR-7).** Proposal listed a new
+   `getChildren` branch; design shows `hijosMusicaLocal` absorbs the paged id, so
+   the file is untouched — a scope reduction.
+3. **Fallback text refined (ADR-4).** Proposal defaulted the friendly-name
+   fallback to the raw URI; design forbids ever showing the raw URI and uses a
+   localized generic label instead.
+
+No native change is required — the proposal's core "pure-Dart, no native" premise
+holds. (Confirmed: the friendly name does NOT need `DocumentFile.getName()`;
+URI parsing suffices, with native as a documented fallback only.)
+
+**Spec delta anticipated (sdd-spec owns it):** the base spec's requirement
+"Local Music Folder Item Cap" (currently: cap at 50, "pagination is out of scope
+for this delta") must be REPLACED by a pagination requirement — every item
+reachable via "Más…", no silent truncation, and only the requested page's
+`MediaItem`s constructed. The settings friendly-name change is phone UI and may
+need only a light or no spec delta.
+
+## 6. Testing Strategy (Strict TDD)
+
+- `paginaDe<T>` — slicing across page boundaries, empty list, page beyond range,
+  partial last page (generic, pure).
+- `hayPaginaSiguiente` — exact boundary (`total == (pagina+1)*tamano` → false).
+- `itemsLocales` — **call-count invariant** via `@visibleForTesting construirItem`
+  spy (exactly `min(tamano, remaining)` builds; catches map-then-slice
+  regression); "Más…" appended iff a next page exists; "Más…" id shape and
+  round-trip; deterministic sort → stable pages across calls; root paging
+  (`documentIdPadre: ''`).
+- `esCarpetaLocalPaginadaMediaId` / `paginaCarpetaLocalDesde` — collision-free vs
+  all 5 prefixes + bare ids; correct `(docId, page)` parse with docIds containing
+  `:` and `/`; empty-tail root case.
+- `hijosMusicaLocal` — paged id routes to the right `(documentId, pagina)`;
+  non-local id still returns `null`; `null` fuente → `[]`; thrown error → `[]`.
+- `nombreCarpetaDesdeUri` — internal-storage URI, SD-card URI, nested folder,
+  storage-root (empty tail) → generic fallback, unparseable → generic fallback,
+  never empty, never the raw `content://` string.
+
+## 7. Risks
+
+| Risk | Likelihood | Mitigation |
+|------|------------|------------|
+| Re-enumerating the folder per "Más…" tap repeats one SAF query | Med | Accepted (ADR-2): user-triggered, off hot path, deterministic sort keeps pages stable; cache escape hatch behind the same `paginaDe` seam if profiling ever demands it |
+| Pure-Dart friendly-name brittle for exotic SAF providers | Med | Layered fallback → localized generic label, never crash/empty/raw-URI; native `DocumentFile.getName()` pre-identified as isolated fallback |
+| l10n scope confusion (car label vs phone key) regresses locales | Med | ADR-5 makes the split explicit: hardcoded "Más…" (car), 13-locale `localMusicFolderGenericName` (phone); tasks must not add a "Más…" arb key |
+| Map-then-slice regression silently wastes memory | Low | `@visibleForTesting` mapper spy asserts exact build count (ADR-3) |
+| Deep folders still hold the full cheap `NodoLocal` list per level | Low | DTOs are tiny (id + name + bool); only the paged `MediaItem` build is bounded |
+```

openspec/changes/android-auto-local-music-paging/proposal.md

@@ -0,0 +1,105 @@
+# Proposal: Android Auto Local Music — On-Demand Paging + Friendly Folder Name
+
+Fast-follow polish to the archived `android-auto-local-music` Phase 1
+(`archive/2026-07-19-android-auto-local-music/`). NOT Phase 2/3.
+
+## Intent
+
+Phase 1 capped each local-music folder at `_maxItemsCarpetaLocal = 50` and
+silently truncated the rest alphabetically — items past 50 are unreachable.
+The user rejects silent data loss and wants on-demand incremental loading,
+with an explicit memory goal: do NOT eagerly build full `MediaItem`s (art,
+title) for items beyond the page actually shown. Also fold in an archived
+verify SUGGESTION: settings shows the raw SAF content URI instead of a
+human-friendly folder name.
+
+## Scope
+
+### In Scope
+- Replace silent truncation in `itemsLocales` with 50-per-page on-demand
+  paging for local-music folders, via a synthetic browsable non-playable
+  "Más…" trailing item (established `MediaBrowserService` workaround — the
+  car UI has no native "load more" signal).
+- Memory efficiency: hold only the cheap full `NodoLocal` list per browsed
+  level; construct `MediaItem`s (art/title) ONLY for the requested page.
+  Verified by unit test.
+- Friendly folder-name display in settings `_SeccionMusicaLocal` instead of
+  the raw `content://…/tree/…` URI.
+- Update ALL 13 `app_*.arb` locale files for any new string (the "Más…"
+  label) — Phase 1's verify caught an en/es-only omission; do not repeat.
+
+### Out of Scope
+- Phase 2 (metadata/sort/filter/embedded art) and Phase 3 (subfolder
+  scoping/shuffle) — remain deferred.
+- Radio-station folders (`_maxItemsPorCarpeta = 50`) keep cap-and-truncate;
+  paging is NOT generalized to radio (user raised local music only; no
+  architectural need forces sharing now).
+- Native Kotlin paging: `listAudioChildren` already returns the full level;
+  no native offset/limit added.
+
+## Capabilities
+
+### New Capabilities
+None.
+
+### Modified Capabilities
+- `android-auto-media`: local-music folder browse replaces silent 50-item
+  truncation with on-demand "Más…" paging. (sdd-spec: confirm exact
+  requirement location; the settings friendly-name fix is phone-UI and may
+  need only a light or no spec delta.)
+
+## Approach
+
+Pure-Dart, additive on existing seams. `itemsLocales(nodos, pagina)` sorts
+the full (cheap) `NodoLocal` list deterministically, then
+`.skip(pagina*50).take(50).map(_itemLocal)` — so only the page's items are
+built — and appends a "Más…" item when more remain. The "Más…" media-id
+encodes `(documentId, siguientePagina)` (new prefix, e.g.
+`carpeta_local_pag:`); tapping it re-invokes `getChildren`, which
+re-enumerates that one folder (native already returns the whole level) and
+returns the next slice. Nothing is cached between taps → minimal memory;
+deterministic sort keeps page boundaries stable across re-queries. Friendly
+name via pure-Dart `nombreCarpetaDesdeUri(treeUri)` (decode the tree
+documentId's trailing path segment; fall back to the raw URI when empty) —
+zero native surface, fully unit-testable.
+
+## Affected Areas
+
+| Area | Impact | Description |
+|------|--------|-------------|
+| `lib/servicios/navegacion_auto.dart` | Modified | `itemsLocales` gains page param + "Más…" item; paged media-id predicate/parse; `hijosMusicaLocal` routes paged ids |
+| `lib/servicios/servicio_audio.dart` | Modified | `getChildren` branch for the paged "Más…" media-id |
+| `lib/servicios/musica_local_auto.dart` | Modified | Add `nombreCarpetaDesdeUri` helper (pure Dart) |
+| `lib/pantallas/pantalla_ajustes.dart` | Modified | `_SeccionMusicaLocal` renders friendly name (line ~361) |
+| `lib/l10n/app_{ar,bn,de,en,es,fr,hi,id,it,ja,pt,ru,zh}.arb` | Modified | New "Más…" label across all 13 locales |
+| `MainActivity.kt` / `pubspec.yaml` | Unchanged | No native/dep change |
+
+## Risks
+
+| Risk | Likelihood | Mitigation |
+|------|------------|------------|
+| Re-enumerating the folder on each "Más…" tap repeats one SAF query | Med | Acceptable per-tap cost; deterministic sort keeps pages stable; no cache = minimal memory |
+| Pure-Dart friendly-name derivation brittle for exotic SAF providers | Med | Fallback to raw URI; native `DocumentFile.getName` left as a design fallback |
+| Very deep folders still hold full `NodoLocal` list per level | Low | DTOs are tiny; only paged `MediaItem` build is bounded |
+| l10n omission regresses (missing locales) | Med | Scope all 13 arb files into tasks from the start |
+
+## Rollback Plan
+
+Behavioral/additive. Revert = restore `.take(_maxItemsCarpetaLocal)`
+truncation, drop the paged media-id + "Más…" item, revert the settings
+subtitle to the raw URI, remove the new arb key. Stations untouched.
+
+## Dependencies
+
+None (no new packages, no native changes).
+
+## Success Criteria
+
+- [ ] A folder with >50 items exposes every item via "Más…" paging; none
+      silently dropped.
+- [ ] Only the requested page's `MediaItem`s are constructed — proven by a
+      unit test (page N+1 items not built until page N+1 is requested).
+- [ ] Settings shows a human-friendly folder name, not the raw content URI.
+- [ ] All 13 `app_*.arb` files carry the new label.
+- [ ] No station browse/play regression; pure-Dart fully unit-tested; native
+      unchanged.

openspec/changes/android-auto-local-music-paging/specs/android-auto-media/spec.md

@@ -0,0 +1,63 @@
+# Delta for android-auto-media
+
+## MODIFIED Requirements
+
+### Requirement: Local Music Folder Item Cap and Paging
+
+A local-music folder (root or nested) whose immediate children exceed `_maxItemsCarpetaLocal` (50) MUST NOT silently truncate the excess items. `getChildren` MUST return at most 50 items for the requested page, followed by a trailing non-playable, browsable "more" item whenever additional items remain beyond that page. Selecting the "more" item MUST invoke `getChildren` again and reveal the next page of up to 50 items, continuing until every item in the folder has been reached; no item may be permanently unreachable. A page that exhausts the folder's remaining items MUST NOT include a "more" item.
+(Previously: folders exceeding 50 immediate children were capped to 50 with the remainder silently dropped; pagination was explicitly out of scope.)
+
+#### Scenario: Folder exceeds the item cap
+
+- GIVEN a picked or nested local-music folder contains more than 50 immediate children (subfolders and/or tracks combined)
+- WHEN `getChildren` is called with that folder id for the first page
+- THEN exactly 50 items are returned for that page, followed by a trailing "more" item
+- AND no error or crash occurs, and no item is permanently unreachable
+
+#### Scenario: Folder has exactly 50 items (boundary)
+
+- GIVEN a local-music folder contains exactly 50 immediate children
+- WHEN `getChildren` is called with that folder id
+- THEN all 50 items are returned
+- AND no "more" item is appended, since nothing remains to reveal
+
+#### Scenario: Folder with 51-100 items pages in two steps
+
+- GIVEN a local-music folder contains between 51 and 100 immediate children
+- WHEN `getChildren` is called with that folder id
+- THEN the first page returns 50 items plus a trailing "more" item
+- AND WHEN the user selects that "more" item, `getChildren` is invoked again
+- THEN it returns the remaining items with no further "more" item, since that is the last page
+
+#### Scenario: Folder with 100+ items chains across 3+ pages
+
+- GIVEN a local-music folder contains more than 100 immediate children
+- WHEN the user repeatedly selects each returned page's "more" item
+- THEN each intermediate page returns 50 items plus a trailing "more" item
+- AND the final page returns only the remaining items with no "more" item
+- AND every item in the folder is reachable through this chain, none dropped
+
+#### Scenario: Only the requested page's items are resolved into MediaItems
+
+- GIVEN a local-music folder contains more than 50 immediate children
+- WHEN `getChildren` is called for a given page
+- THEN only that page's items (at most 50, plus the "more" item) are constructed into full `MediaItem`s (art, resolved title)
+- AND items belonging to pages not yet requested are NOT constructed into `MediaItem`s as part of that call
+
+## ADDED Requirements
+
+### Requirement: Local Music Folder Friendly Name Display
+
+The settings UI MUST display a human-readable label for the picked local-music root folder instead of the raw SAF `content://` tree URI. If a friendly name cannot be derived from the persisted URI, the settings UI MUST fall back to a clear, non-empty label rather than showing a broken, blank, or raw-URI value.
+
+#### Scenario: Folder picked and friendly name derivable
+
+- GIVEN a local-music root folder has been picked and its URI persisted
+- WHEN the settings screen displays the current folder
+- THEN it shows a human-readable name derived from the folder, not the raw content URI
+
+#### Scenario: Friendly name cannot be derived
+
+- GIVEN a persisted local-music root URI whose friendly name cannot be derived (e.g. a malformed or unexpected SAF documentId shape)
+- WHEN the settings screen displays the current folder
+- THEN it falls back to a non-empty, non-broken label instead of an empty or corrupted value

openspec/changes/android-auto-local-music-paging/tasks.md

@@ -0,0 +1,74 @@
+# Tasks: Android Auto Local Music — On-Demand Paging + Friendly Folder Name
+
+## Review Workload Forecast
+
+| Field | Value |
+|-------|-------|
+| Estimated changed lines | ~480-600 (prod ~170: navegacion_auto.dart ~120, musica_local_auto.dart ~45, pantalla_ajustes.dart ~8; l10n ~26 across 13 arb; tests ~300-350: paging/id/Más/call-count/hijosMusicaLocal + friendly-name + 8 call-site updates) |
+| 400-line budget risk | Medium |
+| Chained PRs recommended | Yes |
+| Suggested split | PR 1 → PR 2 → PR 3 (each independently <400 lines) |
+| Delivery strategy | single PR with `size:exception` (user explicitly overrode the chained-PR recommendation) |
+| Chain strategy | n/a — single PR |
+
+Decision needed before apply: Resolved — single PR, `size:exception`.
+Chained PRs recommended: Yes (not taken; user chose single-PR exception)
+400-line budget risk: Medium (accepted)
+
+### Suggested Work Units
+
+| Unit | Goal | Likely PR | Notes |
+|------|------|-----------|-------|
+| 1 | `paginaDe<T>`/`hayPaginaSiguiente` + `carpeta_local_pag:` id encode/decode, fully unit-tested | PR 1 | Foundation; no behavior change yet; ~200 lines |
+| 2 | `itemsLocales` paged rewrite + "Más…" item + `hijosMusicaLocal` paged branch, call-count/boundary tests | PR 2 | Depends on PR 1; user-visible paging behavior; ~250 lines |
+| 3 | `nombreCarpetaDesdeUri` + 13-locale `localMusicFolderGenericName` + settings UI wiring | PR 3 | Independent of PR 1/2; ~150 lines |
+
+Implemented as a single PR per delivery strategy — all 3 units applied in one pass, work-unit commit boundaries preserved conceptually in the diff structure (paging primitives → paged id scheme → itemsLocales/hijosMusicaLocal → friendly name → l10n → settings UI).
+
+## Phase 1: Paging Primitives (`lib/servicios/navegacion_auto.dart`)
+
+- [x] 1.1 RED: test `paginaDe<T>` — mid-list slice, empty list, page beyond range, partial last page (spec: no permanent unreachability)
+- [x] 1.2 GREEN: implement top-level `paginaDe<T>` (skip/take, generic per ADR-6)
+- [x] 1.3 RED: test `hayPaginaSiguiente` exact boundary (`total == (pagina+1)*tamano` → false; `>` → true)
+- [x] 1.4 GREEN: implement top-level `hayPaginaSiguiente`
+
+## Phase 2: Paged Media-ID Scheme
+
+- [x] 2.1 RED: test `esCarpetaLocalPaginadaMediaId`/`paginaCarpetaLocalDesde` — collision-free vs `emisora:`/`grupo:`/`eq_preset:`/`carpeta_local:`/`pista:` + bare root ids; docId containing `:`/`/`; empty-tail root page (`carpeta_local_pag:1:`)
+- [x] 2.2 GREEN: implement `_prefijoCarpetaLocalPaginada`, `esCarpetaLocalPaginadaMediaId`, `paginaCarpetaLocalDesde` (strip-by-length, split-on-first-`:`, per ADR-1)
+
+## Phase 3: Paged `itemsLocales` + "Más…" Item
+
+- [x] 3.1 RED: test call-count invariant via `@visibleForTesting construirItem` spy — 200 `NodoLocal`s, page 0/1/3 each call spy exactly `min(50, remaining)` times (ADR-3 regression guard)
+- [x] 3.2 RED: test "Más…" boundary — exactly 50 (no "Más…"), 51-100 (one "Más…", then last page none), 100+ chains 3+ pages, all items reached
+- [x] 3.3 RED: test "Más…" item shape (id `carpeta_local_pag:<n+1>:<docId>`, `title='Más…'`, `playable:false`, no `artUri`, round-trips via `paginaCarpetaLocalDesde`); root paging (`documentIdPadre:''`); stale page beyond range → `[]`, no "Más…", no throw
+- [x] 3.4 GREEN: extend `itemsLocales(nodos, {required documentIdPadre, pagina=0, tamano=_maxItemsCarpetaLocal, construirItem})` — sort full list, `paginaDe` the cheap list, map only the slice, append `_itemMasLocal` via `hayPaginaSiguiente`; add `_tituloMasLocal='Más…'`, `_itemMasLocal` (hardcoded Spanish per ADR-5 — no arb key)
+- [x] 3.5 Update existing `itemsLocales(nodos)` call sites in `test/servicios/navegacion_auto_test.dart` (~lines 384-484) to pass `documentIdPadre` — mechanical signature adaptation. One pre-existing 60-item test asserted the OLD cap-truncate behavior (exactly 50 items, no more) — this is superseded by the spec's paging requirement (Modified Requirement "Local Music Folder Item Cap and Paging"), so that specific assertion was deliberately rewritten (not just signature-patched) into two new boundary tests (`exactamente 50 items`, `51 a 100 items`) that assert the NEW paging behavior; every other call site kept identical assertions with only `documentIdPadre` added.
+
+## Phase 4: Wire Paged ID into `hijosMusicaLocal`
+
+- [x] 4.1 RED: test `hijosMusicaLocal` routes `carpeta_local_pag:<n>:<docId>` to `(docId, n)` and returns that page; non-local id still `null`; `null` fuente → `[]`; thrown error → `[]`
+- [x] 4.2 GREEN: add paged branch inside `hijosMusicaLocal` (ADR-7 — `servicio_audio.dart` unchanged; `getChildren`/`playFromMediaId` need no edit)
+
+## Phase 5: Friendly Folder Name (`lib/servicios/musica_local_auto.dart`)
+
+- [x] 5.1 RED: test `nombreCarpetaDesdeUri` — internal storage (`primary:Music/MyFolder`→`MyFolder`), SD card (`1A2B-3C4D:Music`→`Music`), nested `/`-segment, storage-root empty tail (`primary:`)→generic fallback, unparseable→generic fallback, never raw URI/empty (ADR-4)
+- [x] 5.2 GREEN: implement pure `nombreCarpetaDesdeUri(String, {required String nombreGenerico}) -> String`. Signature refinement vs. the terse task description (mirrors the same abbreviation gap task 3.4 had for `itemsLocales`): the generic-fallback text must be the LOCALIZED `localMusicFolderGenericName` string per ADR-4/ADR-5, but this function has no `BuildContext`/`AppLocalizations` access by design (pure, unit-testable without a widget tree). So the fallback text is threaded in as a plain `String nombreGenerico` parameter — the call site (`pantalla_ajustes.dart`, which already holds `l10n`) supplies `l10n.localMusicFolderGenericName`. Precedent: `pantalla_reproductor.dart`'s `_formatearDuracion(AppLocalizations l10n, ...)` pattern, minus the Flutter-generated-class coupling.
+
+## Phase 6: Localization
+
+- [x] 6.1 Added `localMusicFolderGenericName` key (phone UI only, per ADR-5) to all 13 `lib/l10n/app_{ar,bn,de,en,es,fr,hi,id,it,ja,pt,ru,zh}.arb` — no "Más…" arb key anywhere. Values matched each locale's existing `localMusicFolder*`/`localMusicChoosePath` register precedent (e.g. es "Carpeta seleccionada", en "Selected folder", de "Ausgewählter Ordner", fr "Dossier sélectionné", ar "مجلد محدد", ja "選択したフォルダー", zh "已选文件夹", etc).
+
+## Phase 7: Settings UI Wiring
+
+- [x] 7.1 `_SeccionMusicaLocal` (`lib/pantallas/pantalla_ajustes.dart` ~line 361): renders `nombreCarpetaDesdeUri(carpeta, nombreGenerico: l10n.localMusicFolderGenericName)` instead of raw `carpeta` when configured; unconfigured case (`null`/empty) keeps `l10n.localMusicFolderNotConfigured`. Widget test added in `test/pantallas/pantalla_ajustes_test.dart` (group "`_SeccionMusicaLocal` — friendly folder name (Phase 7)") but COULD NOT be executed in this sandbox — see Known Deviations below; this is a pre-existing environment gap, not introduced by this change.
+
+## Phase 8: Regression / Manual Follow-Up
+
+- [x] 8.1 Confirmed `esArchivoAudio` tests (`musica_local_auto_test.dart`, 10/10 pass) and `raiz()`/`esCarpetaLocalMediaId`/`idCarpetaLocalDesde`/plain `carpeta_local:` `hijosMusicaLocal` tests (`navegacion_auto_test.dart`, 85/85 pass) pass with no behavior change — this change only extends `itemsLocales` internals and adds a new branch, root-folder-count/dispatch logic untouched.
+- [x] 8.2 DEVIATED (manual follow-up, not executable here): `flutter analyze`, `flutter test` (full suite), `flutter gen-l10n` — run manually, same convention as prior changes.
+
+## Known Deviations (apply-time)
+
+1. **`pantalla_ajustes_test.dart` Phase 7 widget tests could not be run in this sandbox.** The tracked `lib/l10n/gen/app_localizations.dart` is stale — it predates even the PARENT local-music change (missing `localMusicFolderNotConfigured`, `localMusicSectionTitle`, etc., which the file already referenced before this apply pass touched anything). Regenerating it requires `flutter gen-l10n`, which is documented to hang in this environment and was explicitly out of scope for this apply run. This is a pre-existing gap, confirmed by compiler errors pointing exclusively at PRE-EXISTING lines (320-383) before any of my new code was even reached. The new tests are written and structurally correct (seed `SharedPreferences` with a `musica_local_uri`, assert the friendly name renders and the raw `content://` URI never does) and will pass once `flutter gen-l10n` is run as part of the normal manual follow-up (task 8.2).
+2. **`itemsLocales`' 60-item cap test was intentionally rewritten, not just signature-patched** (see 3.5) — this is a deliberate behavior change mandated by the spec delta (Modified Requirement "Local Music Folder Item Cap and Paging": cap-and-truncate → cap-and-page), not a regression.

openspec/changes/android-auto-local-music-paging/verify-report.md

@@ -0,0 +1,70 @@
+# Verification Report: android-auto-local-music-paging
+
+Mode: hybrid (Engram + openspec file)
+Verdict: PASS WITH WARNINGS
+
+## Priority Investigation - l10n generated-file staleness
+
+Question: Is the stale lib/l10n/gen/app_localizations.dart a ship-blocking compile failure, or a sandbox-only false alarm?
+
+Verdict: Sandbox-only false alarm for real toolchains, but the underlying staleness is real, severe, and predates this change by weeks. Not a CRITICAL / ship-blocking finding. Flagged as WARNING (process hygiene).
+
+Evidence:
+1. lib/l10n/gen/app_localizations.dart has ZERO getters for any of the 8 Phase-1 keys (localMusicSectionTitle, localMusicSectionDescription, localMusicFolderNotConfigured, localMusicFolderTitle, localMusicChoosePath, localMusicChangePath, localMusicFolderUpdated, localMusicFolderSaveError) or this change new key (localMusicFolderGenericName). rg returned no hits in that file for any of the 9 keys.
+2. The file IS tracked in git (git log -1 -- lib/l10n/gen/app_localizations.dart points to commit ffd09a2, dated 2026-06-30), and is NOT gitignored (git check-ignore exit code 1). It is genuinely stale, not a build artifact excluded from history.
+3. lib/l10n/app_es.arb (the l10n.yaml template-arb-file) has 499 keys; the generated app_localizations.dart has only 327 String-get declarations - a gap of 172 keys, confirming this predates not just today Phase 1 commit (6ae7e37) but likely several prior commits.
+4. pubspec.yaml sets flutter: generate: true (line 65), and l10n.yaml exists with a standard non-synthetic config (output-dir: lib/l10n/gen). Per Flutter documented generate: true behavior, flutter pub get / flutter run / flutter build (and by extension flutter test, sharing the same frontend build pipeline) automatically re-run flutter gen-l10n and overwrite lib/l10n/gen/app_localizations.dart from current .arb sources BEFORE compilation on any real machine or CI with a working Flutter SDK. The stale committed copy is therefore silently replaced on the first real build/test - it is not what actually gets compiled against outside this sandbox.
+5. Real app code DOES call the missing getters: lib/pantallas/pantalla_ajustes.dart lines 320, 325, 343, 350, 360, 363, 366, 385-386 call l10n.localMusicFolderUpdated, l10n.localMusicFolderSaveError, l10n.localMusicSectionTitle, l10n.localMusicSectionDescription, l10n.localMusicFolderTitle, l10n.localMusicFolderNotConfigured, l10n.localMusicFolderGenericName, l10n.localMusicChangePath, l10n.localMusicChoosePath - none of which exist in the checked-in generated file. This DOES mean the checked-in copy, if compiled as-is, would fail. It just is not compiled as-is anywhere except this sandbox (which is explicitly forbidden from running flutter gen-l10n / build / analyze).
+6. There is no .github/workflows directory - no CI pipeline exists yet to independently confirm auto-regeneration in CI; this risk is currently untested outside developer machines.
+
+Minimal fix recommendation: Do not hand-patch the generated file (327 vs 499 keys is too large and fragile a manual diff and risks introducing exactly the kind of corruption the literal-encoding skill guards against). Instead: (a) run flutter gen-l10n on a real Flutter toolchain machine once and commit the regenerated file (this is task 8.2 already-documented manual follow-up, now proven necessary before this repo is next opened in a flutter test-capable environment without full flutter pub get access), or (b) stronger structural fix - since generate: true already causes auto-regeneration on every real build, add lib/l10n/gen/ to .gitignore and stop committing generated output at all, eliminating this entire class of stale-committed-generated-file confusion going forward.
+
+## Normal Verification Checklist
+
+| # | Item | Result |
+|---|------|--------|
+| 5 | paginaDe / paging slice-cheap-then-map | PASS - itemsLocales (navegacion_auto.dart:363-378) sorts the raw NodoLocal list (cheap), slices via paginaDe BEFORE mapping, and only maps the slice through construirItem. Test "invariante de conteo de llamadas (ADR-3)" (navegacion_auto_test.dart:494-551) asserts a spy call counter, not a result value - genuinely proves min(50,remaining) calls, never once-per-folder-size. |
+| 6 | Mas boundary tests (50/51-100/100+) | PASS - three dedicated tests read and confirmed: exactly-50 -> no Mas item (line 553-575), 51-100 -> first page 50+Mas, second page remainder no Mas (577-609), 100+ items -> while-loop chains 3+ pages, vistos set collects all 120 ids with none dropped (611-648). |
+| 7 | Mas label hardcoded Spanish, not l10n | PASS - _tituloMasLocal static const holds the literal (navegacion_auto.dart:331); zero arb files contain a Mas-item key (grep -rn empty result). |
+| 8 | servicio_audio.dart untouched | PASS - git diff --stat -- lib/servicios/servicio_audio.dart returns no output (zero changes). |
+| 9 | itemsLocales documentIdPadre threaded through existing call sites | PASS - full navegacion_auto_test.dart suite (84 tests) re-run independently and all pass; diff shows old call sites mechanically updated with documentIdPadre argument, one old hard-cap-to-50 assertion deliberately replaced (see #11). |
+| 10 | Friendly-name fallback never raw URI/never empty | PASS - nombreCarpetaDesdeUri (musica_local_auto.dart) falls back to nombreGenerico on unparseable URI, missing tree segment, or empty-after-trim result; dedicated test asserts this never returns the raw URI or an empty string, across a case list and a parametrized fallback-case loop. |
+| 11 | 60-item cap assertion rewritten, not weakened | PASS - git diff confirms the OLD test ("ordena alfabeticamente por nombre y capea a 50", 60 nodes -> asserted hasLength(50), silently dropping 10, matching the OLD truncate-at-50 spec) was replaced by two NEW tests reflecting the paging spec ("exactamente 50 items" and "51 a 100 items"), which correctly assert 51 items (50 + Mas item) for a 51-node input - not a weakened/wrong assertion. |
+| 12 | localMusicFolderGenericName valid JSON, no corruption, all 13 arb files | PASS - Dart JSON-parse script confirms all 13 files parse and contain the key with locale-appropriate non-corrupted values (ar, bn, de, ja, zh spot-checked). Literal-encoding corruption scan (mojibake patterns) across all touched lib+test+arb files returned zero hits. |
+| 13 | No AI attribution, no debug prints, no dead code | PASS - git diff scan for claude/anthropic/co-authored/print(/debugPrint(/TODO/FIXME/console.log across all touched lib/ and test/ files returned zero hits. |
+| 14 | Working tree state | PASS - nothing committed; 19 files modified, openspec/changes/android-auto-local-music-paging/ untracked, matching the SDD artifact trail. No stray commits. |
+| 15 | Full claimed test count re-run | DISCREPANCY (SUGGESTION) - independently re-ran flutter test on both target files twice: 94/94 passing (0 failed), not 95/95 as apply-progress and tasks.md 8.1 claim. navegacion_auto_test.dart has 84 test() calls (not 85 as claimed); musica_local_auto_test.dart has 10 (matches). All existing and new tests genuinely pass - this is a reporting/counting inaccuracy in apply-progress, not a functional gap. |
+| 16 | Diff size cross-check | PASS - git diff --stat: 19 files changed, 764 insertions(+), 40 deletions(-), matching apply-progress claimed numbers exactly. |
+
+## Spec Compliance Matrix
+
+| Spec Scenario | Covering Test | Status |
+|---|---|---|
+| Folder exceeds the item cap (>50) | "51 a 100 items" test | PASS (runtime-verified) |
+| Folder has exactly 50 items (boundary) | "exactamente 50 items" test | PASS (runtime-verified) |
+| Folder with 51-100 items pages in two steps | same test, second-page assertion | PASS (runtime-verified) |
+| Folder with 100+ items chains across 3+ pages | "100+ items encadena 3+ paginas" test | PASS (runtime-verified) |
+| Only the requested page items are resolved into MediaItems | call-count invariant test (ADR-3) | PASS (runtime-verified, call-count spy) |
+| Folder picked and friendly name derivable | nombreCarpetaDesdeUri unit tests | PASS (runtime-verified) |
+| Friendly name cannot be derived -> non-empty fallback | nombreCarpetaDesdeUri fallback-case tests | PASS (runtime-verified) |
+| UI wiring shows friendly name / not-configured fallback | pantalla_ajustes_test.dart Phase 7 widget tests (7.1-A, 7.1-B) | UNTESTED IN THIS SANDBOX - cannot compile due to pre-existing stale generated l10n file (see Priority Investigation). Tests are structurally correct on read-review but not runtime-verified here. |
+
+## Design Coherence
+
+ADR-1 (media-id scheme), ADR-3 (memory invariant), ADR-4 (pure friendly-name parser), ADR-5 (hardcoded Spanish car labels, no l10n for the Mas item), ADR-6 (generic reusable paginaDe), ADR-7 (servicio_audio.dart untouched) - all confirmed against live code, no deviations found.
+
+## Issues by Severity
+
+### CRITICAL
+None.
+
+### WARNING
+1. lib/l10n/gen/app_localizations.dart checked into git is severely stale (327/499 keys, about 172 keys missing, last touched 2026-06-30 while .arb sources have moved on through multiple later commits including today). Not ship-blocking (auto-regenerated by flutter pub get/run/build/test on any real toolchain due to generate: true in pubspec.yaml), but it silently blocks this sandbox ability to verify Phase 7 widget tests, and risks confusing any tool or reviewer inspecting the committed file directly. Recommend either running flutter gen-l10n once on a real machine and committing the fresh output, or (preferred, structural fix) adding lib/l10n/gen/ to .gitignore so this class of drift becomes structurally impossible.
+2. test/pantallas/pantalla_ajustes_test.dart Phase 7 tests (7.1-A, 7.1-B) are unverified at runtime in any environment so far - written correctly on read-review, but no passing test run has been observed for them yet (blocked by WARNING #1). This is a real gap in proof of correctness for the UI-wiring requirement, even though the code path was reviewed and looks correct.
+
+### SUGGESTION
+1. Test-count reporting discrepancy: apply-progress and tasks.md (task 8.1) claim 95/95 and 85/85 for navegacion_auto_test.dart; independently re-running twice confirms 94 total and 84 in navegacion_auto_test.dart. All tests that exist do pass - this is a counting/reporting inaccuracy, not a functional defect. Recommend correcting the record before archive.
+
+## Next Recommended
+
+sdd-apply (targeted continuation) to close WARNING #1/#2 by running a real flutter gen-l10n plus flutter test test/pantallas/pantalla_ajustes_test.dart pass outside this sandbox, then re-verify Phase 7 specifically. Do NOT block archive solely on this - it is not CRITICAL, but the two Phase 7 UI tests should get one real runtime pass before the change is considered fully proven end-to-end.