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).

test/pantallas/pantalla_ajustes_test.dart

@@ -64,6 +64,7 @@ void main() {
   Future<EstadoRadio> crearEstado({
     bool eqMultiDeviceEnabled = false,
     Map<String, PresetEcualizador> presetsDispositivo = const {},
+    FakeServicioDispositivoAudio? dispositivoAudio,
   }) async {
     final estado = EstadoRadio(
       audio: FakeServicioAudio(),
@@ -76,6 +77,7 @@ void main() {
       servicioGrabacion: _FakeGrabacion(),
       resolverArchivoCustom: _archivoCustomVacio,
       iniciarAutomaticamente: false,
+      dispositivoAudio: dispositivoAudio,
     );
     await estado.ecualizador.cargarPersistido();
     return estado;
@@ -99,6 +101,7 @@ void main() {
     Map<String, PresetEcualizador>? presetsDispositivo,
     Map<String, String>? nombresDispositivos,
     String? activeDeviceId,
+    String nombrePlataforma = 'BT Speaker',
   }) async {
     final fakeDispositivo = activeDeviceId != null
         ? (FakeServicioDispositivoAudio()
@@ -106,7 +109,7 @@ void main() {
               DispositivoAudio(
                 id: activeDeviceId,
                 tipo: TipoDispositivo.bluetoothA2dp,
-                nombre: 'BT Speaker',
+                nombre: nombrePlataforma,
               ),
             ))
         : null;
@@ -380,6 +383,134 @@ void main() {
       );
     });
   });
+
+  // ── bt-device-identity Phase 4: display fix + permission trigger ─────────
+
+  group('_SeccionEcualizadorAvanzado — bt-device-identity Phase 4', () {
+    // 4.1 — new behavior: the cached platform name (not '') now feeds
+    // nombreVisible, so a device with no custom rename shows its real name.
+    testWidgets('4.1 platform name displays with no custom rename', (
+      tester,
+    ) async {
+      setLargeSurface(tester);
+      _suppressListTileInkAssertion();
+      const deviceId = 'bt_a2dp:AA:BB:CC:DD:EE:FF';
+      final estado = await crearEstadoConNombres(
+        presetsDispositivo: {deviceId: PresetEcualizador.rock},
+        activeDeviceId: deviceId,
+        nombrePlataforma: 'AirPods Pro',
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(buildAjustes(estado));
+      await pumpStable(tester);
+
+      await tester.scrollUntilVisible(
+        find.text('Known audio devices'),
+        300,
+        scrollable: find.byType(Scrollable).first,
+      );
+      await pumpStable(tester);
+
+      expect(find.text('AirPods Pro'), findsOneWidget);
+      expect(find.text(deviceId), findsNothing);
+    });
+
+    // 4.4 — triangulation companion: custom rename still wins even though
+    // the row now also has a cached platform name available.
+    testWidgets('4.4 custom rename overrides platform name', (tester) async {
+      setLargeSurface(tester);
+      _suppressListTileInkAssertion();
+      const deviceId = 'bt_a2dp:AA:BB:CC:DD:EE:FF';
+      final estado = await crearEstadoConNombres(
+        presetsDispositivo: {deviceId: PresetEcualizador.rock},
+        activeDeviceId: deviceId,
+        nombrePlataforma: 'AirPods Pro',
+        nombresDispositivos: {deviceId: 'My Headphones'},
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(buildAjustes(estado));
+      await pumpStable(tester);
+
+      await tester.scrollUntilVisible(
+        find.text('Known audio devices'),
+        300,
+        scrollable: find.byType(Scrollable).first,
+      );
+      await pumpStable(tester);
+
+      expect(find.text('My Headphones'), findsOneWidget);
+      expect(find.text('AirPods Pro'), findsNothing);
+    });
+
+    // 4.5 — approval test (regression-lock): a device never seen on the
+    // stream has no cached platform name, so legacy raw-id fallback holds.
+    testWidgets('4.5 no platform name yet falls back to raw id', (
+      tester,
+    ) async {
+      setLargeSurface(tester);
+      _suppressListTileInkAssertion();
+      const deviceId = 'bt_a2dp:AA:BB:CC:DD:EE:FF';
+      final estado = await crearEstadoConNombres(
+        presetsDispositivo: {deviceId: PresetEcualizador.rock},
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(buildAjustes(estado));
+      await pumpStable(tester);
+
+      await tester.scrollUntilVisible(
+        find.text('Known audio devices'),
+        300,
+        scrollable: find.byType(Scrollable).first,
+      );
+      await pumpStable(tester);
+
+      expect(find.text(deviceId), findsOneWidget);
+    });
+
+    // 4.6 — permission trigger point: turning the toggle ON requests
+    // BLUETOOTH_CONNECT; turning it back OFF must not re-fire the request.
+    testWidgets('4.6 permission call fires on device-management open', (
+      tester,
+    ) async {
+      setLargeSurface(tester);
+      _suppressListTileInkAssertion();
+      final fakeDispositivo = FakeServicioDispositivoAudio();
+      final estado = await crearEstado(
+        eqMultiDeviceEnabled: false,
+        dispositivoAudio: fakeDispositivo,
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(buildAjustes(estado));
+      await pumpStable(tester);
+
+      await tester.scrollUntilVisible(
+        find.text('Advanced Equalization Options'),
+        300,
+        scrollable: find.byType(Scrollable).first,
+      );
+      await pumpStable(tester);
+
+      expect(fakeDispositivo.solicitarPermisoBluetoothCalls, equals(0));
+
+      // Toggle ON: permission requested exactly once.
+      await tester.tap(find.byType(Switch).last);
+      await pumpStable(tester);
+
+      expect(estado.ecualizador.eqMultiDeviceEnabled, isTrue);
+      expect(fakeDispositivo.solicitarPermisoBluetoothCalls, equals(1));
+
+      // Toggle OFF again: no further permission request.
+      await tester.tap(find.byType(Switch).last);
+      await pumpStable(tester);
+
+      expect(estado.ecualizador.eqMultiDeviceEnabled, isFalse);
+      expect(fakeDispositivo.solicitarPermisoBluetoothCalls, equals(1));
+    });
+  });
 }
 
 // ── Infrastructure ──────────────────────────────────────────────────────────