fix(devices): cache platform device names, dedupe placeholder ids, purge collided EQ entries

Dart half of bt-device-identity. EstadoEcualizador now caches each
device's platform-reported name in memory so the settings screen
shows the device's own Bluetooth name instead of its raw id when no
custom rename exists, and skips auto-creating preset entries for the
composite-placeholder sentinel. Enabling multi-device EQ triggers the
Bluetooth permission request through the new channel contract. A
flag-guarded one-time migration purges only entries keyed by the
exact literal placeholder id from the three per-device preference
maps, since those collided entries cannot be attributed to a device.

Work unit 2/2 of bt-device-identity (Dart state + migration).

lib/estado/estado_ecualizador.dart

@@ -26,6 +26,12 @@ import '../servicios/servicio_ecualizador.dart';
 /// When the toggle is false, resolution falls back to the original 2-level
 /// hierarchy (station → global) — zero behavioral change vs. prior releases.
 class EstadoEcualizador extends ChangeNotifier {
+  /// Composite-placeholder id prefix (bt-device-identity ADR-6): marks a
+  /// device whose real Bluetooth MAC is not yet known (BLUETOOTH_CONNECT
+  /// denied or unresolved). Devices with this prefix still update the
+  /// platform-name cache but never auto-create a `presetsDispositivo` entry.
+  static const _prefijoPlaceholderCompuesto = 'bt_a2dp:name:';
+
   EstadoEcualizador({
     required this.audio,
     ServicioEcualizador? servicio,
@@ -54,6 +60,13 @@ class EstadoEcualizador extends ChangeNotifier {
   /// Custom display names for devices: deviceId → custom name.
   final Map<String, String> _nombresDispositivos = {};
 
+  /// Last-seen platform (Bluetooth/productName) name per deviceId.
+  ///
+  /// In-memory only (bt-device-identity ADR-4) — NOT persisted. Devices
+  /// re-report their name on every enumeration, so this cache self-heals
+  /// every session without needing a SharedPreferences key or migration.
+  final Map<String, String> _nombresPlataforma = {};
+
   PresetEcualizador _presetPrincipal = PresetEcualizador.flat;
   PresetEcualizador _presetActual = PresetEcualizador.flat;
   bool _activo = true;
@@ -210,15 +223,27 @@ class EstadoEcualizador extends ChangeNotifier {
   Future<void> _onDispositivoCambiado(DispositivoAudio dispositivo) async {
     if (!_eqMultiDeviceEnabled) return;
 
+    // Cache updates on every event regardless of whether a preset entry
+    // gets created below (bt-device-identity ADR-4).
+    _nombresPlataforma[dispositivo.id] = dispositivo.nombre;
     _dispositivoActualId = dispositivo.id;
 
     // First-seen device: copy the current resolved preset as its starting
     // point. builtin_speaker is excluded: it must always fall through to
     // the hierarchy (L4 global) instead of being pinned by a forced L3
     // device-level copy, otherwise a later global-preset change would be
-    // masked by this stale entry for the base device.
+    // masked by this stale entry for the base device. Composite-placeholder
+    // ids are also excluded (bt-device-identity ADR-6): they are transient
+    // fallback ids for a device whose real MAC is not yet known, so
+    // persisting a preset entry for them would create dead noise that never
+    // resolves to the eventual real-MAC id.
     final esBase = dispositivo.tipo == TipoDispositivo.altavozInterno;
-    if (!esBase && !_presetsDispositivo.containsKey(dispositivo.id)) {
+    final esPlaceholderCompuesto = dispositivo.id.startsWith(
+      _prefijoPlaceholderCompuesto,
+    );
+    if (!esBase &&
+        !esPlaceholderCompuesto &&
+        !_presetsDispositivo.containsKey(dispositivo.id)) {
       final presetBase = _resolverPresetActivo();
       _presetsDispositivo[dispositivo.id] = presetBase;
       await servicio.guardarPresetDispositivo(dispositivo.id, presetBase);
@@ -252,6 +277,21 @@ class EstadoEcualizador extends ChangeNotifier {
     if (notificar) notifyListeners();
   }
 
+  /// Requests `BLUETOOTH_CONNECT` (API 31+) at the point the
+  /// device-management UI is opened (bt-device-identity ADR-1).
+  ///
+  /// Thin passthrough to the injected device service so callers don't need
+  /// [ServicioDispositivoAudio] wired as its own top-level `Provider` (Task
+  /// 4.8 — `ServicioDispositivoAudio` is only ever constructed inside
+  /// `EstadoRadio` today, not exposed via the provider tree; routing through
+  /// here avoids adding wiring the tree doesn't already have). Returns false
+  /// when no device service is injected.
+  Future<bool> solicitarPermisoBluetooth() async {
+    final svc = _dispositivoAudio;
+    if (svc == null) return false;
+    return svc.solicitarPermisoBluetooth();
+  }
+
   Future<void> cambiarPresetPrincipal(
     PresetEcualizador preset, {
     bool notificar = true,
@@ -353,6 +393,11 @@ class EstadoEcualizador extends ChangeNotifier {
   String obtenerNombreDispositivo(String deviceId) =>
       _nombresDispositivos[deviceId] ?? '';
 
+  /// Returns the last-seen platform name for [deviceId], or an empty string
+  /// if none has been observed yet (bt-device-identity ADR-4).
+  String nombrePlataforma(String deviceId) =>
+      _nombresPlataforma[deviceId] ?? '';
+
   /// Resolves the display name for [deviceId] using the fallback chain:
   /// custom name → [platformName] → raw [deviceId].
   String nombreVisible(String deviceId, String platformName) {

lib/pantallas/pantalla_ajustes.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:io';
 
 import 'package:file_picker/file_picker.dart';
@@ -698,7 +699,8 @@ class _SeccionEcualizadorAvanzado extends StatelessWidget {
                   child: GestureDetector(
                     behavior: HitTestBehavior.translucent,
                     onTap:
-                        () => eq.cambiarMultiDeviceEnabled(!multiDeviceEnabled),
+                        () =>
+                            _alternarMultiDevice(eq, !multiDeviceEnabled),
                     child: Column(
                       crossAxisAlignment: CrossAxisAlignment.start,
                       children: [
@@ -718,7 +720,7 @@ class _SeccionEcualizadorAvanzado extends StatelessWidget {
                 Switch.adaptive(
                   value: multiDeviceEnabled,
                   onChanged:
-                      (habilitado) => eq.cambiarMultiDeviceEnabled(habilitado),
+                      (habilitado) => _alternarMultiDevice(eq, habilitado),
                 ),
               ],
             ),
@@ -749,6 +751,17 @@ class _SeccionEcualizadorAvanzado extends StatelessWidget {
       ),
     );
   }
+
+  /// Toggles the multi-device EQ feature and, when turning it ON, requests
+  /// `BLUETOOTH_CONNECT` at this point-of-intent (bt-device-identity ADR-1)
+  /// so BT devices report their real MAC instead of the OS placeholder.
+  /// Fire-and-forget: neither call blocks the toggle UI on its result.
+  void _alternarMultiDevice(EstadoEcualizador eq, bool habilitado) {
+    unawaited(eq.cambiarMultiDeviceEnabled(habilitado));
+    if (habilitado) {
+      unawaited(eq.solicitarPermisoBluetooth());
+    }
+  }
 }
 
 /// A single device row in the known-devices list.
@@ -766,7 +779,7 @@ class _FilaDispositivo extends StatelessWidget {
     final l10n = AppLocalizations.of(context);
     final eq = context.watch<EstadoEcualizador>();
     final isActive = eq.dispositivoActualId == deviceId;
-    final displayName = eq.nombreVisible(deviceId, '');
+    final displayName = eq.nombreVisible(deviceId, eq.nombrePlataforma(deviceId));
 
     return Padding(
       padding: const EdgeInsets.symmetric(vertical: 6),
@@ -843,7 +856,10 @@ class _DialogoEdicionDispositivoState
   void initState() {
     super.initState();
     final eq = context.read<EstadoEcualizador>();
-    final displayName = eq.nombreVisible(widget.deviceId, '');
+    final displayName = eq.nombreVisible(
+      widget.deviceId,
+      eq.nombrePlataforma(widget.deviceId),
+    );
     _nombreCtrl = TextEditingController(text: displayName);
     _presetActual = widget.preset;
   }

lib/servicios/servicio_dispositivo_audio.dart

@@ -21,6 +21,12 @@ abstract class ServicioDispositivoAudio {
   /// (method channel round-trip). Returns the cached value if already known.
   Future<DispositivoAudio> obtenerDispositivoActual();
 
+  /// Requests the `BLUETOOTH_CONNECT` runtime permission (API 31+) at the
+  /// point the device-management UI is opened (bt-device-identity ADR-1).
+  /// Returns true when granted or not required (SDK < 31, iOS); false when
+  /// denied.
+  Future<bool> solicitarPermisoBluetooth();
+
   /// Cancels the device-change subscription and releases resources.
   Future<void> dispose();
 }
@@ -82,6 +88,14 @@ class ServicioDispositivoAudioReal extends ServicioDispositivoAudio {
     return device;
   }
 
+  @override
+  Future<bool> solicitarPermisoBluetooth() async {
+    final granted = await _methodChannel.invokeMethod<bool>(
+      'requestBluetoothConnect',
+    );
+    return granted ?? false;
+  }
+
   @override
   Future<void> dispose() async {
     await _eventSub?.cancel();

lib/servicios/servicio_ecualizador.dart

@@ -43,6 +43,13 @@ class ServicioEcualizador {
   static const _keyPresetsMatriz = 'eq_presets_matriz_v1';
   static const _keyNombresDispositivos = 'eq_nombres_dispositivos_v1';
 
+  /// bt-device-identity ADR-5: guard flag for the one-time placeholder purge.
+  static const _keyPlaceholderPurgaHecha = 'eq_placeholder_purge_done_v1';
+
+  /// bt-device-identity ADR-3: the exact OS placeholder MAC, in the
+  /// `bt_a2dp:`-prefixed id shape used across all device-keyed SP maps.
+  static const _placeholderMacLiteral = 'bt_a2dp:02:00:00:00:00:00';
+
   final SharedPreferences? _prefs;
 
   /// Injected startup instance (S3-R4); getInstance() is only a fallback.
@@ -50,6 +57,7 @@ class ServicioEcualizador {
       _prefs ?? SharedPreferences.getInstance();
 
   Future<ConfiguracionEcualizador> cargar() async {
+    await migrarClavesPlaceholder();
     final prefs = await _resolverPrefs();
     final principal = _leerPresetPrincipal(prefs);
     final porEmisora = _leerPresetsPorEmisora(prefs);
@@ -67,6 +75,56 @@ class ServicioEcualizador {
     );
   }
 
+  /// One-time guarded migration (bt-device-identity ADR-5): purges entries
+  /// keyed by the exact OS placeholder MAC ([_placeholderMacLiteral]) from
+  /// all three device-keyed SP maps. Idempotent — short-circuits via
+  /// [_keyPlaceholderPurgaHecha] after the first successful run. Every other
+  /// entry (including near-miss keys) is preserved byte-for-byte.
+  Future<void> migrarClavesPlaceholder() async {
+    final prefs = await _resolverPrefs();
+    if (prefs.getBool(_keyPlaceholderPurgaHecha) ?? false) return;
+
+    final presetsPorDispositivo = _leerMapa(prefs, _keyPresetsPorDispositivo);
+    if (presetsPorDispositivo.remove(_placeholderMacLiteral) != null) {
+      await _guardarMapa(
+        prefs,
+        _keyPresetsPorDispositivo,
+        presetsPorDispositivo,
+      );
+    }
+
+    // Matrix keys are "stationUuid:deviceId"; split on the FIRST colon only
+    // (station UUIDs are RFC4122 and contain no colons — multi-device-eq
+    // ADR-3), since deviceId itself may contain colons (e.g. a MAC-based id).
+    final presetsMatriz = _leerMapa(prefs, _keyPresetsMatriz);
+    final clavesMatrizAPurgar = presetsMatriz.keys.where((clave) {
+      final separador = clave.indexOf(':');
+      if (separador == -1) return false;
+      final deviceIdSegmento = clave.substring(separador + 1);
+      return deviceIdSegmento == _placeholderMacLiteral;
+    }).toList();
+    if (clavesMatrizAPurgar.isNotEmpty) {
+      for (final clave in clavesMatrizAPurgar) {
+        presetsMatriz.remove(clave);
+      }
+      await _guardarMapa(prefs, _keyPresetsMatriz, presetsMatriz);
+    }
+
+    final nombresDispositivos = _leerMapaStrings(
+      prefs,
+      _keyNombresDispositivos,
+    );
+    if (nombresDispositivos.remove(_placeholderMacLiteral) != null) {
+      await _guardarMapaStrings(
+        prefs,
+        _keyNombresDispositivos,
+        nombresDispositivos,
+      );
+    }
+
+    await prefs.setBool(_keyPlaceholderPurgaHecha, true);
+  }
+
   Future<void> guardarPrincipal(PresetEcualizador preset) async {
     final prefs = await _resolverPrefs();
     await prefs.setString(_keyPresetPrincipal, jsonEncode(preset.toJson()));