feat(eq): android auto custom equalizer and robust device detection

- MainActivity: onListen re-emits the current active device and registers
  the audio device callback idempotently, so recreated activities resync
  instead of freezing the active-device id on a disconnected device.
- servicio_dispositivo_audio: resubscribir() re-opens the event channel;
  estado_ecualizador exposes refrescarDispositivoActual() with an
  in-flight guard, invoked on app resume and when opening advanced EQ
  options, clearing stale green-dot device selections.
- navegacion_auto/servicio_audio: new 'Personalizado' browse tree in
  Android Auto (5 band folders, 13 gain steps each) applied live via
  setBanda; preset and gain taps persist at device level when
  multi-device EQ is active and respect station/matrix overrides,
  with apply-before-persist ordering and children-changed notifications.
- l10n: regenerate stale generated localizations; add rxdart as direct
  dependency for the subscribeToChildren override.

lib/servicios/navegacion_auto.dart

@@ -7,12 +7,15 @@ import 'package:flutter/foundation.dart' show visibleForTesting;
 import 'package:path_provider/path_provider.dart';
 
 import '../estado/orden_emisoras.dart';
+import '../modelos/dispositivo_audio.dart';
 import '../modelos/emisora.dart';
 import '../modelos/grupo_favoritos.dart';
 import '../modelos/pista_local.dart';
 import '../modelos/preset_ecualizador.dart';
 import 'musica_local_auto.dart';
 import 'persistencia_tolerante.dart';
+import 'servicio_dispositivo_audio.dart';
+import 'servicio_ecualizador.dart';
 import 'servicio_favoritos.dart';
 
 /// Generic page slice over [items] (Design ADR-6): returns at most [tamano]
@@ -43,6 +46,38 @@ const _prefijoPresetEq = 'eq_preset:';
 /// predicate.
 bool esPresetMediaId(String id) => id.startsWith(_prefijoPresetEq);
 
+/// Custom-EQ band folder media-id prefix (feature auto-custom-eq):
+/// `eq_banda:<indice>`. Collision-free against [_prefijoPresetEq] and
+/// [_prefijoGananciaEq] — the three `eq_` prefixes diverge at index 3
+/// (`b` vs `p` vs `g`), so no `startsWith` check ever matches a sibling's id.
+const _prefijoBandaEq = 'eq_banda:';
+
+/// Whether [id] identifies a custom-EQ band folder (feature auto-custom-eq).
+bool esBandaEqMediaId(String id) => id.startsWith(_prefijoBandaEq);
+
+/// Builds the `eq_banda:<indice>` media id for band [indice] (feature
+/// auto-custom-eq) — single authority for the id shape, shared by the tree
+/// builder and the handler's children-changed notification.
+String idBandaEq(int indice) => '$_prefijoBandaEq$indice';
+
+/// Custom-EQ gain leaf media-id prefix (feature auto-custom-eq):
+/// `eq_gain:<indice>:<db>`. Collision-free against [_prefijoBandaEq] and
+/// [_prefijoPresetEq] (see [_prefijoBandaEq]'s divergence note).
+const _prefijoGananciaEq = 'eq_gain:';
+
+/// Whether [id] identifies a custom-EQ gain leaf item (feature
+/// auto-custom-eq).
+bool esGananciaEqMediaId(String id) => id.startsWith(_prefijoGananciaEq);
+
+/// Number of fixed EQ bands (`PresetEcualizador` asserts exactly 5).
+const _numBandasEq = 5;
+
+/// Frequency labels for the 5 EQ bands, in the same order as
+/// `PresetEcualizador.bandas` (60Hz, 250Hz, 1kHz, 4kHz, 16kHz — the model's
+/// documented band layout, same frequencies the phone's
+/// `EcualizadorWidget._etiquetas` renders).
+const etiquetasBandasEq = ['60 Hz', '250 Hz', '1 kHz', '4 kHz', '16 kHz'];
+
 /// Local-track media-id prefix (Design "media-id scheme"), collision-free
 /// against [_prefijoEmisora], [_prefijoPresetEq], `grupo:` and the bare
 /// folder id constants. Top-level (not a [ConstructorArbolAuto] member),
@@ -208,6 +243,11 @@ class ConstructorArbolAuto {
   /// generic station-list `hijos()` path.
   static const idEcualizador = 'ecualizador';
 
+  /// Browsable "Personalizado" folder id under [idEcualizador] (feature
+  /// auto-custom-eq). Deliberately NOT added to [_idsCarpetas] — routed by
+  /// its own dedicated branch in `getChildren`, like [idEcualizador] itself.
+  static const idEqPersonalizado = 'eq_custom';
+
   /// Root folder id for the local-music browsable root (Design "media-id
   /// scheme"). Deliberately NOT added to [_idsCarpetas] — it has its own
   /// dedicated branch (`hijosMusicaLocal`), not the generic station-list
@@ -736,6 +776,52 @@ class ConstructorArbolAuto {
   List<MediaItem> presetsEq(List<PresetEcualizador> presets) =>
       presets.map(itemPresetEq).toList();
 
+  /// The browsable "Personalizado" folder appended after the fixed preset
+  /// leaves under `Ecualizador` (feature auto-custom-eq). Hardcoded Spanish
+  /// label, matching every other car-tree label in this file — never routed
+  /// through `AppLocalizations` (see [_tituloMasLocal]'s precedent).
+  MediaItem itemEqPersonalizado() =>
+      _carpeta(idEqPersonalizado, 'Personalizado');
+
+  /// The 5 per-band browsable folders under `Personalizado` (feature
+  /// auto-custom-eq): id `eq_banda:<indice>`, title
+  /// `<frecuencia> · <ganancia actual>` (e.g. `'60 Hz · +3 dB'`) so the
+  /// driver sees the effective custom gains at a glance. [actual] is the
+  /// persisted/effective custom preset resolved by the caller
+  /// ([presetPersonalizadoEfectivo]).
+  List<MediaItem> bandasEq(PresetEcualizador actual) => [
+    for (
+      var i = 0;
+      i < actual.bandas.length && i < etiquetasBandasEq.length;
+      i++
+    )
+      _carpeta(
+        idBandaEq(i),
+        '${etiquetasBandasEq[i]} · ${formatearGananciaEq(actual.bandas[i])}',
+      ),
+  ];
+
+  /// The 13 playable gain leaves for band [indice] (feature auto-custom-eq):
+  /// -12..+12 dB in steps of 2, id `eq_gain:<indice>:<db>`. The currently
+  /// selected gain — when it falls on the 2 dB grid — is marked with a
+  /// leading `● ` so the active value is visible while browsing. An
+  /// out-of-range [indice] returns `[]`, never throws.
+  List<MediaItem> gananciasBandaEq(int indice, PresetEcualizador actual) {
+    if (indice < 0 || indice >= actual.bandas.length) return const [];
+    final gananciaActual = actual.bandas[indice];
+    return [
+      for (var db = -12; db <= 12; db += 2)
+        MediaItem(
+          id: '$_prefijoGananciaEq$indice:$db',
+          title:
+              '${db.toDouble() == gananciaActual ? '● ' : ''}'
+              '${formatearGananciaEq(db.toDouble())}',
+          playable: true,
+          extras: _contentStyleGrid,
+        ),
+    ];
+  }
+
   /// Children of the `Favoritos` folder (Design "Ungrouped favorites stay as
   /// direct leaves at the Favoritos root"): non-empty custom-group folders
   /// (phone order, capped at [_maxGruposPorFavoritos]), followed by
@@ -1221,6 +1307,79 @@ PresetEcualizador? resolverPresetEq(String id, List<PresetEcualizador> presets)
   return null;
 }
 
+/// Formats a gain in dB for the Auto tree (feature auto-custom-eq):
+/// explicit `+` for boosts, plain `0 dB` for neutral, ASCII `-` for cuts.
+/// Non-integer factory-preset gains keep one decimal (`'+1.5 dB'`) so band
+/// titles never lie about the effective value.
+String formatearGananciaEq(double db) {
+  final esEntera = db == db.roundToDouble();
+  final valor = esEntera ? db.round().toString() : db.toStringAsFixed(1);
+  return db > 0 ? '+$valor dB' : '$valor dB';
+}
+
+/// Parses an `eq_banda:<indice>` [id] into its band index (feature
+/// auto-custom-eq). Any other shape (no prefix, non-integer, outside the
+/// fixed [_numBandasEq]-band range) returns `null` instead of throwing.
+int? indiceBandaEqDesde(String id) {
+  if (!esBandaEqMediaId(id)) return null;
+  final indice = int.tryParse(id.substring(_prefijoBandaEq.length));
+  if (indice == null || indice < 0 || indice >= _numBandasEq) return null;
+  return indice;
+}
+
+/// Parses an `eq_gain:<indice>:<db>` [id] into its `(indice, db)` pair
+/// (feature auto-custom-eq): the prefix is stripped by length, the remainder
+/// split on its single `:`. Any other shape (no prefix, missing/non-integer
+/// fields, index outside the band range, gain outside -12..+12) returns
+/// `null` instead of throwing.
+(int indice, double db)? gananciaEqDesde(String id) {
+  if (!esGananciaEqMediaId(id)) return null;
+  final resto = id.substring(_prefijoGananciaEq.length);
+  final separador = resto.indexOf(':');
+  if (separador <= 0) return null;
+  final indice = int.tryParse(resto.substring(0, separador));
+  final db = int.tryParse(resto.substring(separador + 1));
+  if (indice == null || db == null) return null;
+  if (indice < 0 || indice >= _numBandasEq) return null;
+  if (db < -12 || db > 12) return null;
+  return (indice, db.toDouble());
+}
+
+/// Persistence-targeting decision for a car EQ action — preset tap or band
+/// change (feature auto-custom-eq): returns the deviceId to persist a
+/// DEVICE-level entry for, or `null` to fall back to the global principal.
+/// `null` cases mirror the phone hierarchy's own exclusions: multi-device
+/// toggle off, unknown device (query failed/timed out — [dispositivo] is
+/// `null`), built-in speaker (must keep falling through to L4 global), and
+/// composite-placeholder BT ids (ADR-6). Pure — testable without platform
+/// channels.
+String? dispositivoDestinoEq({
+  required bool multiDeviceEnabled,
+  required DispositivoAudio? dispositivo,
+}) {
+  if (!multiDeviceEnabled || dispositivo == null) return null;
+  if (dispositivo.tipo == TipoDispositivo.altavozInterno) return null;
+  if (dispositivo.id.startsWith(prefijoPlaceholderBtName)) return null;
+  return dispositivo.id;
+}
+
+/// Resolves the custom-EQ preset the Auto tree displays and edits (feature
+/// auto-custom-eq): the device-level entry for [deviceId] when multi-device
+/// is enabled and one exists, the global principal otherwise. Station/matrix
+/// overrides are deliberately NOT consulted — the `Personalizado` tree
+/// displays and edits exactly the level a gain tap persists to
+/// ([dispositivoDestinoEq]), so what the driver sees is what a tap changes.
+PresetEcualizador presetPersonalizadoEfectivo({
+  required ConfiguracionEcualizador config,
+  required String? deviceId,
+}) {
+  if (config.eqMultiDeviceEnabled && deviceId != null) {
+    final porDispositivo = config.presetsDispositivo[deviceId];
+    if (porDispositivo != null) return porDispositivo;
+  }
+  return config.principal;
+}
+
 /// Pure per-station apply gate (Design ADR-5), mirroring
 /// `EstadoEcualizador.cambiarPresetPrincipal`'s exact logic
 /// (`estado_ecualizador.dart:302-304`): the new principal preset is applied
@@ -1232,16 +1391,46 @@ bool debeAplicarPrincipalAhora({
   required Set<String> clavesPorEmisora,
 }) => uuidActual == null || !clavesPorEmisora.contains(uuidActual);
 
+/// Apply-live gate for a DEVICE-targeted car selection (feature
+/// auto-custom-eq), extending [debeAplicarPrincipalAhora] with the matrix
+/// level of the phone hierarchy: the freshly persisted device-level preset
+/// is audible now unless the current station carries a per-station override
+/// or a `estación:dispositivoDestino` matrix entry shadows it.
+bool debeAplicarSeleccionAhora({
+  required String? uuidActual,
+  required Set<String> clavesPorEmisora,
+  required Set<String> clavesMatriz,
+  required String? deviceIdDestino,
+}) {
+  if (uuidActual == null) return true;
+  if (clavesPorEmisora.contains(uuidActual)) return false;
+  if (deviceIdDestino != null &&
+      clavesMatriz.contains('$uuidActual:$deviceIdDestino')) {
+    return false;
+  }
+  return true;
+}
+
 /// Orchestrates an `eq_preset:<nombre>` selection from the car (Design
 /// "Data flow — a preset tap", ADR-3): resolves [id] via [resolverPresetEq],
-/// persists it as principal via [persistirPrincipal], and conditionally
-/// applies it live via [aplicar] when [debeAplicarPrincipalAhora] allows it.
+/// persists it, and conditionally applies it live via [aplicar].
+///
+/// Persistence targeting (feature auto-custom-eq): when the optional
+/// [dispositivoDestino]/[persistirDispositivo] seams are provided and the
+/// destination resolves to a deviceId ([dispositivoDestinoEq]'s decision),
+/// the preset is persisted as a DEVICE-level entry — so the car selection
+/// sticks for the car's output device instead of being shadowed by the
+/// hierarchy's L3 lookup — and the live application is gated by
+/// [debeAplicarSeleccionAhora]. Otherwise (seams omitted, or destination
+/// `null`: toggle off, built-in, placeholder, query error/timeout) the
+/// original global path runs unchanged: [persistirPrincipal] +
+/// [debeAplicarPrincipalAhora].
 ///
 /// This function's signature exposes ONLY the EQ persist/apply seams — it
 /// has NO parameter for `playMediaItem`, `mediaItem`, or `playbackState`, so
 /// there is no code path from a preset tap to playback (Design ADR-3,
 /// non-playback invariant enforced structurally, not by discipline). An
-/// unknown/stale [id] is a no-op: neither seam is invoked and no exception
+/// unknown/stale [id] is a no-op: no seam is invoked and no exception
 /// propagates (Spec "Unknown or stale preset id").
 Future<void> aplicarPresetPorMediaId(
   String id, {
@@ -1250,9 +1439,34 @@ Future<void> aplicarPresetPorMediaId(
   required Future<Set<String>> Function() clavesPorEmisora,
   required Future<void> Function(PresetEcualizador) persistirPrincipal,
   required Future<void> Function(PresetEcualizador) aplicar,
+  Future<String?> Function()? dispositivoDestino,
+  Future<void> Function(String deviceId, PresetEcualizador preset)?
+  persistirDispositivo,
+  Future<Set<String>> Function()? clavesMatriz,
 }) async {
   final preset = resolverPresetEq(id, presets);
   if (preset == null) return;
+
+  final destino =
+      (dispositivoDestino == null || persistirDispositivo == null)
+          ? null
+          : await dispositivoDestino();
+  if (destino != null) {
+    // Apply-first ordering: if the live application throws, nothing has
+    // been persisted yet, so audible and persisted state cannot diverge.
+    if (debeAplicarSeleccionAhora(
+      uuidActual: uuidActual,
+      clavesPorEmisora: await clavesPorEmisora(),
+      clavesMatriz:
+          clavesMatriz == null ? const <String>{} : await clavesMatriz(),
+      deviceIdDestino: destino,
+    )) {
+      await aplicar(preset);
+    }
+    await persistirDispositivo!(destino, preset);
+    return;
+  }
+
   await persistirPrincipal(preset);
   if (debeAplicarPrincipalAhora(
     uuidActual: uuidActual,
@@ -1262,6 +1476,75 @@ Future<void> aplicarPresetPorMediaId(
   }
 }
 
+/// Orchestrates an `eq_gain:<indice>:<db>` selection from the car (feature
+/// auto-custom-eq): parses [id] via [gananciaEqDesde], resolves the custom
+/// base preset for the persistence target ([presetPersonalizadoEfectivo]
+/// over [cargarConfig]'s snapshot), replaces the single band (the result is
+/// always named `Personalizado` via `copyWithBandas`), persists it at DEVICE
+/// level when [dispositivoDestino] yields a deviceId — global principal
+/// otherwise, including the headless error/timeout fallback — and applies
+/// the band live via [aplicarBanda] (the handler's `setBanda`, itself a
+/// no-op while the EQ engine is unavailable).
+///
+/// Live application is gated by [debeAplicarSeleccionAhora] over the same
+/// optional [uuidActual]/[clavesPorEmisora]/[clavesMatriz] seams as
+/// [aplicarPresetPorMediaId] (omitted seams keep the legacy always-apply
+/// behavior), and runs BEFORE persistence so a throwing apply cannot leave
+/// persisted and audible state divergent.
+///
+/// Same non-playback structural invariant as [aplicarPresetPorMediaId]: no
+/// playback seam exists in this signature. A malformed/out-of-range [id] or
+/// a failing [cargarConfig] degrades to a no-op — no seam is invoked and no
+/// exception propagates.
+Future<void> aplicarGananciaPorMediaId(
+  String id, {
+  required Future<ConfiguracionEcualizador> Function() cargarConfig,
+  required Future<String?> Function() dispositivoDestino,
+  required Future<void> Function(String deviceId, PresetEcualizador preset)
+  persistirDispositivo,
+  required Future<void> Function(PresetEcualizador preset) persistirPrincipal,
+  required Future<void> Function(int indice, double db) aplicarBanda,
+  String? uuidActual,
+  Future<Set<String>> Function()? clavesPorEmisora,
+  Future<Set<String>> Function()? clavesMatriz,
+}) async {
+  final ganancia = gananciaEqDesde(id);
+  if (ganancia == null) return;
+  final (indice, db) = ganancia;
+
+  final ConfiguracionEcualizador config;
+  try {
+    config = await cargarConfig();
+  } catch (_) {
+    return;
+  }
+
+  final destino = await dispositivoDestino();
+  final base = presetPersonalizadoEfectivo(config: config, deviceId: destino);
+  final bandas = List<double>.from(base.bandas);
+  bandas[indice] = db;
+  final modificado = base.copyWithBandas(bandas);
+
+  // Apply-first ordering (same rationale as [aplicarPresetPorMediaId]'s
+  // device branch): a throwing apply must not leave persisted state ahead
+  // of the audible one.
+  if (debeAplicarSeleccionAhora(
+    uuidActual: uuidActual,
+    clavesPorEmisora:
+        clavesPorEmisora == null ? const <String>{} : await clavesPorEmisora(),
+    clavesMatriz:
+        clavesMatriz == null ? const <String>{} : await clavesMatriz(),
+    deviceIdDestino: destino,
+  )) {
+    await aplicarBanda(indice, db);
+  }
+  if (destino != null) {
+    await persistirDispositivo(destino, modificado);
+  } else {
+    await persistirPrincipal(modificado);
+  }
+}
+
 /// 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