feat(auto): browsable Android Auto media tree with play-by-id [size:exception]

Expose PluriWave to Android Auto (projected) as a media app:

- Declare car media support (automotive_app_desc.xml + manifest meta-data)
  so Android Auto discovers the existing MediaBrowserService.
- New navegacion_auto.dart: ConstructorArbolAuto builds the browse tree
  (Favoritos / Todas las emisoras / Mis emisoras, 50-item cap, stable
  emisora:<id> media ids), reproducirPorMediaId routes a car tap to the
  existing playMediaItem pipeline, FuenteEmisorasAutoLocal serves the tree
  cold-start-safe (local favorites/custom stations before Flutter UI runs).
- PluriWaveAudioHandler overrides getChildren/getMediaItem/playFromMediaId
  as thin delegations; playback pipeline untouched.
- EstadoRadio pushes live station snapshots to the browse source and
  reconciles the selected station when playback starts from the car.
- Every playable item ships title + artUri; stations without logo fall
  back to a bundled default art (android.resource://).

Tests: 52/52 green (10 new navegacion_auto, 2 new estado_radio, plus
audio safety-net suites). Handler overrides and native XML are
static-review-only (no Android build env). Size exception approved for a
single reviewable commit.

lib/servicios/navegacion_auto.dart

@@ -0,0 +1,265 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:audio_service/audio_service.dart';
+import 'package:path_provider/path_provider.dart';
+
+import '../estado/orden_emisoras.dart';
+import '../modelos/emisora.dart';
+import 'persistencia_tolerante.dart';
+import 'servicio_favoritos.dart';
+
+/// URI of the bundled default station artwork, served from
+/// `android/app/src/main/res/drawable` via `android.resource://` (Design
+/// "default artwork delivery" — no per-URI grant needed, works offline, and
+/// cannot 404 unlike a FileProvider content URI or a remote placeholder).
+const String _defaultArtUri =
+    'android.resource://es.freetimelab.pluriwave/drawable/default_station_art';
+
+const _prefijoEmisora = 'emisora:';
+
+/// Browse-source abstraction for the Android Auto media tree (Design
+/// "getChildren data source, cold-start safe"). Kept separate from
+/// `EstadoRadio` so a headless Auto bind (`main()` runs but the widget tree
+/// — and therefore the lazily-created `EstadoRadio` — never builds) still
+/// gets a valid, non-throwing tree.
+abstract class FuenteEmisorasAuto {
+  Future<List<Emisora>> favoritos();
+  Future<List<Emisora>> misEmisoras();
+
+  /// `populares` snapshot; may be empty on a cold bind (Design "which
+  /// stations surface & ordering").
+  Future<List<Emisora>> todas();
+  Future<Emisora?> porUuid(String uuid);
+
+  /// Live-snapshot push (Design "live snapshot the source prefers"):
+  /// `EstadoRadio`, when alive, calls this unconditionally on every
+  /// favorites/custom/populares mutation so a car and phone that are both
+  /// live see identical lists. Default no-op — only implementations that
+  /// actually buffer a snapshot (e.g. [FuenteEmisorasAutoLocal]) need to
+  /// override it; a null field on `EstadoRadio` skips the call entirely via
+  /// `?.`.
+  void actualizarSnapshot({
+    List<Emisora>? favoritos,
+    List<Emisora>? misEmisoras,
+    List<Emisora>? todas,
+  }) {}
+}
+
+/// Pure builder for the Android Auto browse tree: folders, leaf items, id
+/// resolution. No platform dependency — fully testable without a running
+/// car or a real `AudioHandler`.
+class ConstructorArbolAuto {
+  /// Root folder ids (Design "media-id scheme"). The tree root itself is
+  /// identified by [AudioService.browsableRootId], not by a constant here —
+  /// the handler compares against it directly before calling [raiz].
+  static const idFavoritos = 'favoritos';
+  static const idTodas = 'todas';
+  static const idMisEmisoras = 'mis_emisoras';
+
+  static const _idsCarpetas = {idFavoritos, idTodas, idMisEmisoras};
+  static const _maxItemsPorCarpeta = 50;
+
+  /// Content-style extras (Design "content style", optional polish): list
+  /// (1) for the root's folders, grid (2) for playable station items.
+  static const _contentStyleLista = {
+    'android.media.browse.CONTENT_STYLE_BROWSABLE_HINT': 1,
+    'android.media.browse.CONTENT_STYLE_PLAYABLE_HINT': 1,
+  };
+  static const _contentStyleGrid = {
+    'android.media.browse.CONTENT_STYLE_PLAYABLE_HINT': 2,
+  };
+
+  /// The 3 root folders (Favoritos, Todas las emisoras, Mis emisoras), all
+  /// non-playable.
+  List<MediaItem> raiz() => [
+    _carpeta(idFavoritos, 'Favoritos'),
+    _carpeta(idTodas, 'Todas las emisoras'),
+    _carpeta(idMisEmisoras, 'Mis emisoras'),
+  ];
+
+  MediaItem _carpeta(String id, String titulo) => MediaItem(
+    id: id,
+    title: titulo,
+    playable: false,
+    extras: _contentStyleLista,
+  );
+
+  /// Leaf items for [parentId], sorted via [ordenarEmisoras] and capped at
+  /// [_maxItemsPorCarpeta] (Design "which stations surface & ordering" —
+  /// avoids driver distraction and Auto list limits). Unknown [parentId]
+  /// (or an empty [emisoras]) returns an empty list instead of throwing.
+  List<MediaItem> hijos(String parentId, {required List<Emisora> emisoras}) {
+    if (!_idsCarpetas.contains(parentId)) return const [];
+    if (emisoras.isEmpty) return const [];
+    final ordenadas = ordenarEmisoras(emisoras, OrdenEmisoras.calidad);
+    return ordenadas.take(_maxItemsPorCarpeta).map(itemEmisora).toList();
+  }
+
+  /// Maps a single [Emisora] to a playable `MediaItem`: id `emisora:<uuid>`
+  /// (Design "media-id scheme"), title, and artUri with the default-art
+  /// fallback (Design "default artwork delivery").
+  MediaItem itemEmisora(Emisora e) => MediaItem(
+    id: '$_prefijoEmisora${e.uuid}',
+    title: e.nombre,
+    playable: true,
+    artUri: Uri.parse(_artUriPara(e)),
+    extras: _contentStyleGrid,
+  );
+
+  String _artUriPara(Emisora e) {
+    final favicon = e.favicon;
+    return (favicon != null && favicon.isNotEmpty) ? favicon : _defaultArtUri;
+  }
+
+  /// Resolves `emisora:<uuid>` ids to the matching [Emisora] in [universo].
+  /// Any other shape (no prefix, empty uuid, unmatched uuid) returns `null`
+  /// instead of throwing (Spec "Media Item Resolution by ID").
+  Emisora? resolver(String id, List<Emisora> universo) {
+    if (!id.startsWith(_prefijoEmisora)) return null;
+    final uuid = id.substring(_prefijoEmisora.length);
+    if (uuid.isEmpty) return null;
+    for (final emisora in universo) {
+      if (emisora.uuid == uuid) return emisora;
+    }
+    return null;
+  }
+}
+
+/// Routing seam between a car-tapped `emisora:<uuid>` media id and the
+/// existing internal playback path (Design "playback coherence" — reuse
+/// over duplication). Resolves the uuid via [fuente], builds the same
+/// phone-shaped `MediaItem` (`id` = station url, `extras['uuid']`) that
+/// [ServicioAudio.reproducir] builds, and delegates to [reproducir].
+///
+/// A stale/unknown id (or a malformed one) is a no-op: [reproducir] is
+/// never called and no exception propagates (Spec "Unknown or stale media
+/// id").
+Future<void> reproducirPorMediaId(
+  String id, {
+  required FuenteEmisorasAuto fuente,
+  required Future<void> Function(MediaItem) reproducir,
+}) async {
+  if (!id.startsWith(_prefijoEmisora)) return;
+  final uuid = id.substring(_prefijoEmisora.length);
+  if (uuid.isEmpty) return;
+
+  final emisora = await fuente.porUuid(uuid);
+  if (emisora == null) return;
+
+  final item = MediaItem(
+    id: emisora.url,
+    title: emisora.nombre,
+    artist: emisora.pais ?? '',
+    album: 'PluriWave',
+    artUri:
+        emisora.favicon != null && emisora.favicon!.isNotEmpty
+            ? Uri.tryParse(emisora.favicon!)
+            : null,
+    extras: {'uuid': emisora.uuid},
+  );
+  await reproducir(item);
+}
+
+/// Local, cold-start-safe implementation of [FuenteEmisorasAuto] (Design
+/// "getChildren data source"). Reads favourites from SQLite and custom
+/// stations from the tolerant JSON file directly — both loadable without
+/// the network or a built widget tree, unlike `EstadoRadio._init()` (which
+/// is lazy-created by `ChangeNotifierProvider.create:` and may never run on
+/// a headless Auto bind). `EstadoRadio`, when alive, overrides these reads
+/// with a live snapshot via [actualizarSnapshot].
+class FuenteEmisorasAutoLocal implements FuenteEmisorasAuto {
+  FuenteEmisorasAutoLocal({
+    ServicioFavoritos? favoritosServicio,
+    Future<String> Function()? resolverRutaCustom,
+  }) : _favoritosServicio = favoritosServicio ?? ServicioFavoritos(),
+       _resolverRutaCustom = resolverRutaCustom;
+
+  final ServicioFavoritos _favoritosServicio;
+  final Future<String> Function()? _resolverRutaCustom;
+
+  List<Emisora>? _snapshotFavoritos;
+  List<Emisora>? _snapshotMisEmisoras;
+  List<Emisora>? _snapshotTodas;
+
+  /// Overrides the next reads with `EstadoRadio`'s live in-memory lists
+  /// (Design "live snapshot the source prefers"). Passing `null` for a
+  /// field leaves its current override (or local read) untouched.
+  @override
+  void actualizarSnapshot({
+    List<Emisora>? favoritos,
+    List<Emisora>? misEmisoras,
+    List<Emisora>? todas,
+  }) {
+    if (favoritos != null) _snapshotFavoritos = favoritos;
+    if (misEmisoras != null) _snapshotMisEmisoras = misEmisoras;
+    if (todas != null) _snapshotTodas = todas;
+  }
+
+  @override
+  Future<List<Emisora>> favoritos() async {
+    final snapshot = _snapshotFavoritos;
+    if (snapshot != null) return snapshot;
+    try {
+      return await _favoritosServicio.obtenerTodos();
+    } catch (_) {
+      // Cold-start safety (Spec "Browse requested before app state is
+      // loaded"): never throw out of a browse call.
+      return const [];
+    }
+  }
+
+  @override
+  Future<List<Emisora>> misEmisoras() async {
+    final snapshot = _snapshotMisEmisoras;
+    if (snapshot != null) return snapshot;
+    return _leerEmisorasCustom();
+  }
+
+  @override
+  Future<List<Emisora>> todas() async {
+    // No live network snapshot on a cold bind — populated only once
+    // EstadoRadio pushes its populares list (Design "which stations
+    // surface & ordering": degrades gracefully to empty-but-valid).
+    return _snapshotTodas ?? const [];
+  }
+
+  @override
+  Future<Emisora?> porUuid(String uuid) async {
+    final listas = await Future.wait([favoritos(), misEmisoras(), todas()]);
+    for (final lista in listas) {
+      for (final emisora in lista) {
+        if (emisora.uuid == uuid) return emisora;
+      }
+    }
+    return null;
+  }
+
+  /// Mirrors `EstadoRadio._cargarEmisorasCustom()`'s tolerant JSON read:
+  /// missing/corrupt files never throw, they degrade to an empty list.
+  Future<List<Emisora>> _leerEmisorasCustom() async {
+    try {
+      final ruta = await _rutaArchivoCustom();
+      final archivo = File(ruta);
+      if (!await archivo.exists()) return const [];
+      final contenido = await archivo.readAsString();
+      final data = jsonDecode(contenido) as List;
+      final resultado = parseListaTolerante<Emisora>(
+        data,
+        Emisora.fromMap,
+        subsistema: 'emisoras_custom_auto',
+        coleccion: 'emisoras_custom',
+      );
+      return resultado.validas;
+    } catch (_) {
+      return const [];
+    }
+  }
+
+  Future<String> _rutaArchivoCustom() async {
+    final resolver = _resolverRutaCustom;
+    if (resolver != null) return resolver();
+    final dir = await getApplicationDocumentsDirectory();
+    return '${dir.path}/emisoras_custom.json';
+  }
+}

lib/servicios/servicio_audio.dart

@@ -11,6 +11,7 @@ import '../l10n/gen/app_localizations.dart';
 import '../modelos/emisora.dart';
 import '../modelos/preset_ecualizador.dart';
 import 'controlador_reconexion.dart';
+import 'navegacion_auto.dart';
 import 'servicio_audio_session.dart';
 
 /// Estado de reproducción expuesto al UI.
@@ -35,6 +36,16 @@ void registrarHandler(PluriWaveAudioHandler handler) {
   _handlerGlobal = handler;
 }
 
+// ─────────────────────────────────────────────────────────────────────────────
+// Android Auto browse source — registered from main.dart, mirrors
+// registrarHandler above (Design "getChildren data source registration").
+// ─────────────────────────────────────────────────────────────────────────────
+FuenteEmisorasAuto? _fuenteNavegacionGlobal;
+
+void registrarFuenteNavegacion(FuenteEmisorasAuto fuente) {
+  _fuenteNavegacionGlobal = fuente;
+}
+
 /// Wrapper de alto nivel para el UI.
 class ServicioAudio {
   PluriWaveAudioHandler get _handler {
@@ -712,4 +723,84 @@ class PluriWaveAudioHandler extends BaseAudioHandler
       favicon: mediaItem.artUri?.toString(),
     );
   }
+
+  // ── Android Auto browsing (thin delegation to navegacion_auto.dart's
+  // already-tested pure logic — Design "getChildren data source") ─────────
+
+  @override
+  Future<List<MediaItem>> getChildren(
+    String parentMediaId, [
+    Map<String, dynamic>? options,
+  ]) async {
+    try {
+      final constructor = ConstructorArbolAuto();
+      if (parentMediaId == AudioService.browsableRootId) {
+        return constructor.raiz();
+      }
+      final fuente = _fuenteNavegacionGlobal;
+      if (fuente == null) return const [];
+      final emisoras = await _listaParaCarpeta(fuente, parentMediaId);
+      return constructor.hijos(parentMediaId, emisoras: emisoras);
+    } catch (_) {
+      // Spec "Browse requested before app state is loaded": never throw out
+      // of a browse call, even on an unexpected failure.
+      return const [];
+    }
+  }
+
+  @override
+  Future<MediaItem?> getMediaItem(String mediaId) async {
+    try {
+      final fuente = _fuenteNavegacionGlobal;
+      if (fuente == null) return null;
+      final universo = await _universoCompleto(fuente);
+      final constructor = ConstructorArbolAuto();
+      final emisora = constructor.resolver(mediaId, universo);
+      return emisora == null ? null : constructor.itemEmisora(emisora);
+    } catch (_) {
+      return null;
+    }
+  }
+
+  @override
+  Future<void> playFromMediaId(
+    String mediaId, [
+    Map<String, dynamic>? extras,
+  ]) async {
+    final fuente = _fuenteNavegacionGlobal;
+    if (fuente == null) return;
+    try {
+      await reproducirPorMediaId(
+        mediaId,
+        fuente: fuente,
+        reproducir: playMediaItem,
+      );
+    } catch (e) {
+      // Spec "Unknown or stale media id": never propagate from the handler.
+      developer.log(
+        '[PluriWave] Error en playFromMediaId($mediaId): $e',
+        name: 'ServicioAudio',
+        level: 900,
+      );
+    }
+  }
+
+  Future<List<Emisora>> _listaParaCarpeta(
+    FuenteEmisorasAuto fuente,
+    String parentId,
+  ) => switch (parentId) {
+    ConstructorArbolAuto.idFavoritos => fuente.favoritos(),
+    ConstructorArbolAuto.idMisEmisoras => fuente.misEmisoras(),
+    ConstructorArbolAuto.idTodas => fuente.todas(),
+    _ => Future.value(const []),
+  };
+
+  Future<List<Emisora>> _universoCompleto(FuenteEmisorasAuto fuente) async {
+    final listas = await Future.wait([
+      fuente.favoritos(),
+      fuente.misEmisoras(),
+      fuente.todas(),
+    ]);
+    return listas.expand((lista) => lista).toList();
+  }
 }