fix: initialize reminder channel and clarify notification permission diagnostics

mobile/test/services/notification_gateway_test.dart

@@ -7,6 +7,54 @@ import 'package:hepan_everyday/services/local_notification_service.dart';
 
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
+  test('fresh notification initialization creates the course category before checks', () async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.android;
+    AndroidFlutterLocalNotificationsPlugin.registerWith();
+    const channel = MethodChannel('dexterous.com/flutter/local_notifications');
+    const system = MethodChannel('com.tpschedule.app/reminders');
+    final messenger =
+        TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger;
+    final categories = <Map<Object?, Object?>>[];
+    messenger.setMockMethodCallHandler(channel, (call) async {
+      switch (call.method) {
+        case 'initialize':
+          return true;
+        case 'createNotificationChannel':
+          final data = call.arguments as Map;
+          categories.add({
+            ...Map<Object?, Object?>.from(data),
+            // Android returns a numeric color even when no LED was set.
+            'ledColor': data['ledColor'] ?? 0,
+          });
+          return null;
+        case 'getNotificationAppLaunchDetails':
+          return {'notificationLaunchedApp': false};
+        case 'areNotificationsEnabled':
+        case 'canScheduleExactNotifications':
+          return true;
+        case 'getNotificationChannels':
+          return categories;
+        case 'pendingNotificationRequests':
+          return [];
+      }
+      return null;
+    });
+    messenger.setMockMethodCallHandler(
+      system,
+      (_) async => <Object?, Object?>{},
+    );
+    addTearDown(() {
+      debugDefaultTargetPlatformOverride = null;
+      messenger.setMockMethodCallHandler(channel, null);
+      messenger.setMockMethodCallHandler(system, null);
+    });
+    final gateway = PluginReminderGateway();
+    final diagnosis = await gateway.diagnose();
+    expect(diagnosis['channelImportance'], Importance.high.value);
+    expect(diagnosis['appNotificationsEnabled'], isTrue);
+    expect(diagnosis['channelExists'], isTrue);
+    expect(categories.single['id'], 'hepan_lessons');
+  });
   test(
     'querying future reminders does not depend on active notification access',
     () async {

mobile/test/widgets/reminder_tools_test.dart

@@ -70,6 +70,42 @@ Future<void> _open(WidgetTester tester, _Notifications notifications) async {
 }
 
 void main() {
+  testWidgets(
+    'Android 7 does not ask the user to create an unsupported category',
+    (tester) async {
+      final notifications = _Notifications()
+        ..diagnosis = Completer<Map<String, Object?>>();
+      notifications.diagnosis!.complete({
+        'notifications': true,
+        'appNotificationsEnabled': true,
+        'channelExists': false,
+        'system': {'sdk': 24},
+      });
+      await _open(tester, notifications);
+      await tester.tap(find.text('检查提醒'));
+      await tester.pumpAndSettle();
+      expect(find.textContaining('类别尚未建立'), findsNothing);
+      expect(find.text('系统通知总开关：已允许'), findsOneWidget);
+    },
+  );
+  testWidgets(
+    'diagnosis separates the application switch from the reminder category',
+    (tester) async {
+      final notifications = _Notifications()
+        ..diagnosis = Completer<Map<String, Object?>>();
+      notifications.diagnosis!.complete({
+        'notifications': false,
+        'appNotificationsEnabled': false,
+        'channelExists': true,
+        'courseChannelEnabled': true,
+      });
+      await _open(tester, notifications);
+      await tester.tap(find.text('检查提醒'));
+      await tester.pumpAndSettle();
+      expect(find.text('系统通知总开关：未允许'), findsOneWidget);
+      expect(find.text('课前提醒类别：已允许'), findsOneWidget);
+    },
+  );
   testWidgets('test controls distinguish immediate and background reminders', (
     tester,
   ) async {