feat(alarmas): verify native registration after a successful save

android.programar() returning without throwing was treated as proof
the OS registered the alarm -- this is exactly the gap the reported
case fell through. guardarAlarma now cross-checks a fresh native
pending-alarm count against how many alarms Dart believes are
active-with-a-next-run right after a successful schedule call, and
records a failure for the just-saved alarm when the native count
falls short.

FakePuertoAlarmasAndroid.alarmasNativasPendientes now defaults to a
count derived from programar()/cancelar() calls (mirroring the real
native scheduler's own registry) instead of a frozen 0, while any
test that explicitly assigns the field keeps getting exactly that
value regardless of what programar/cancelar do afterward -- verified
against the full suite, no regressions.

lib/estado/estado_alarmas.dart

@@ -118,6 +118,7 @@ class EstadoAlarmas extends ChangeNotifier {
       );
       await android.programar(guardada);
       await _limpiarFalloProgramacion(guardada.id);
+      await _verificarRegistroNativo(guardada.id);
     } catch (e) {
       _error = 'Alarma guardada, pero Android no pudo programarla todavía: $e';
       await _registrarFalloProgramacion(alarma.id);
@@ -221,9 +222,7 @@ class EstadoAlarmas extends ChangeNotifier {
       );
       _aplicar(config);
     } catch (e) {
-      debugPrint(
-        '[PluriWave][alarmas] registrar fallo programacion ERROR $e',
-      );
+      debugPrint('[PluriWave][alarmas] registrar fallo programacion ERROR $e');
     }
   }
 
@@ -239,6 +238,40 @@ class EstadoAlarmas extends ChangeNotifier {
     }
   }
 
+  /// Verifies the OS genuinely registered [alarmaId] after a successful
+  /// `android.programar` call (fix/alarmas-fallos-silenciosos, item 3): a
+  /// scheduling call that returns without throwing is not proof enough by
+  /// itself -- this cross-check against the native pending-alarm count is
+  /// exactly what would have caught the reported "alarm never rings, no
+  /// exception anywhere" case. Compares a FRESH native count against how
+  /// many alarms Dart believes are currently active-with-a-next-run; a
+  /// native count that falls short is recorded as a failure for the alarm
+  /// the user just interacted with. Never overrides an already-caught
+  /// programar() exception (this only runs on ITS success path).
+  Future<void> _verificarRegistroNativo(String alarmaId) async {
+    try {
+      final alarma = _buscarAlarma(alarmaId);
+      if (alarma == null ||
+          !alarma.activa ||
+          alarma.proximaProgramable == null) {
+        return;
+      }
+      final diag = await android.diagnostico();
+      _diagnostico = diag;
+      final esperadas =
+          _alarmas
+              .where((a) => a.activa && a.proximaProgramable != null)
+              .length;
+      if (diag.alarmasNativasPendientes < esperadas) {
+        _error =
+            'Alarma guardada, pero el sistema no confirma que quedó registrada.';
+        await _registrarFalloProgramacion(alarmaId);
+      }
+    } catch (e) {
+      debugPrint('[PluriWave][alarmas] verificar registro nativo ERROR $e');
+    }
+  }
+
   Future<void> cambiarActiva(AlarmaMusical alarma, bool activa) async {
     await guardarAlarma(alarma.copyWith(activa: activa));
   }