fix: initialize reminder channel and clarify notification permission diagnostics

mobile/lib/features/profile/reminder_tools.dart

@@ -69,6 +69,9 @@ class _ReminderToolsState extends State<ReminderTools> {
       'reminderStatus': c.reminderResult.status.name,
       for (final key in [
         'notifications',
+        'appNotificationsEnabled',
+        'channelExists',
+        'courseChannelEnabled',
         'exactAlarm',
         'pendingCount',
         'channelImportance',
@@ -125,8 +128,16 @@ class _ReminderToolsState extends State<ReminderTools> {
     final rawSystem = diagnosis['system'];
     final system = rawSystem is Map ? rawSystem : const {};
     final pending = diagnosis['pendingCount'];
+    final sdk = system['sdk'];
+    final channelsSupported = sdk is! int || sdk >= 26;
     return [
       '通知权限：${_permission(diagnosis['notifications'])}',
+      if (diagnosis['appNotificationsEnabled'] is bool)
+        '系统通知总开关：${_permission(diagnosis['appNotificationsEnabled'])}',
+      if (channelsSupported && diagnosis['channelExists'] == true)
+        '课前提醒类别：${_permission(diagnosis['courseChannelEnabled'])}',
+      if (channelsSupported && diagnosis['channelExists'] == false)
+        '课前提醒类别尚未建立，请重新打开应用后检查。',
       '精确提醒：${_permission(diagnosis['exactAlarm'])}',
       if (pending is int) '待发送提醒：$pending 条',
       if (diagnosis['notifications'] == false) '系统通知已关闭，请在通知设置中开启。',