Fix cached reminder recovery and retain pre-reconcile idle diagnostics

mobile/test/services/notification_service_test.dart

@@ -13,6 +13,15 @@ class AlarmGateway extends ReminderGateway {
   final alarms = <int, ReminderRequest>{};
   int permissionRequests = 0;
   bool dropWrites = false;
+  final missingHandles = <int>{};
+  Set<int> lastAuditedIds = {};
+  int scheduleCalls = 0;
+  @override
+  Future<Set<int>> missingSystemIds(Set<int> ids) async {
+    lastAuditedIds = {...ids};
+    return missingHandles.intersection(ids);
+  }
+
   @override
   Future<ReminderPermissions> permissions({required bool request}) async {
     if (request) permissionRequests++;
@@ -23,7 +32,9 @@ class AlarmGateway extends ReminderGateway {
   Future<Set<int>> pendingIds() async => alarms.keys.toSet();
   @override
   Future<void> schedule(ReminderRequest value) async {
+    scheduleCalls++;
     if (!dropWrites) alarms[value.id] = value;
+    missingHandles.remove(value.id);
   }
 
   @override
@@ -48,6 +59,32 @@ void main() {
     return AppSnapshot.fromJson(json).settings;
   }
 
+  test(
+    'overdue cached reminders are audited before removal on warm resume',
+    () async {
+      final events = ScheduleEngine.occurrences([course()], term);
+      await service.reconcile(events, settings, DateTime.utc(2026, 9, 9));
+      final cached = gateway.alarms.keys.toSet();
+      expect(cached, isNotEmpty);
+      await service.reconcile(events, settings, DateTime.utc(2027, 1, 1));
+      expect(gateway.lastAuditedIds, cached);
+      expect(gateway.alarms, isEmpty);
+    },
+  );
+
+  test('cached fingerprint does not hide a missing system trigger', () async {
+    final events = ScheduleEngine.occurrences([course()], term);
+    final now = DateTime.utc(2026, 9, 9);
+    await service.reconcile(events, settings, now);
+    final previous = gateway.scheduleCalls;
+    gateway.missingHandles.addAll(gateway.alarms.keys);
+    await service.reconcile(events, settings, now);
+    expect(gateway.scheduleCalls, previous + 1);
+    expect(gateway.missingHandles, isEmpty);
+    await service.reconcile(events, settings, now);
+    expect(gateway.scheduleCalls, previous + 1);
+  });
+
   test(
     'does not report success when native scheduling did not persist',
     () async {