docs(openspec): archive android-auto-local-music-paging

Merges its delta requirements into the android-auto-media base spec.
This closes out Phase-1 polish for local music; Phase 2 (metadata,
sort/filter, real art) and Phase 3 (subfolder scoping, shuffle)
remain the only planned future work for this feature.

openspec/specs/android-auto-media/spec.md

@@ -236,16 +236,63 @@ Selecting a `pista:<id>` item MUST resolve to the corresponding `PistaLocal` and
 - WHEN resolution fails
 - THEN playback does not start and no unhandled exception propagates from the handler
 
-### Requirement: Local Music Folder Item Cap
+### Requirement: Local Music Folder Item Cap and Paging
 
-A local-music folder (root or nested) whose immediate children exceed `_maxItemsPorCarpeta` (50) MUST be capped to that limit rather than returning unbounded results; pagination is out of scope for this delta.
+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 at most 50 items are returned, consistent with the existing `_maxItemsPorCarpeta` cap applied to station folders
-- AND no error or crash occurs as a result of the truncation
+- 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
+
+### 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
 
 ### Requirement: Playable Item Metadata