feat: add notifyOnSubtasks setting to control subtask notifications (#227)

* feat: add notifyOnSubtasks setting to control subtask notifications

- Add notifyOnSubtasks toggle in NotificationSettings (moved to general section)
- Update useEventStream.ts to skip notifications for subtasks when disabled
- Add server-side push notification control for subtasks
- Update UI store, persistence, and desktop settings types

* feat: apply notifyOnSubtasks across web push + desktop notifications

---------

Co-authored-by: Jovines <jovines@qq.com>

packages/ui/src/lib/persistence.ts

@@ -216,6 +216,9 @@ const applyDesktopUiPreferences = (settings: DesktopSettings) => {
       store.setNotificationMode(settings.notificationMode);
     }
   }
+  if (typeof settings.notifyOnSubtasks === 'boolean' && settings.notifyOnSubtasks !== store.notifyOnSubtasks) {
+    store.setNotifyOnSubtasks(settings.notifyOnSubtasks);
+  }
   if (typeof settings.toolCallExpansion === 'string'
     && (settings.toolCallExpansion === 'collapsed' || settings.toolCallExpansion === 'activity' || settings.toolCallExpansion === 'detailed')) {
     if (settings.toolCallExpansion !== store.toolCallExpansion) {
@@ -345,6 +348,9 @@ const sanitizeWebSettings = (payload: unknown): DesktopSettings | null => {
   if (typeof candidate.notificationMode === 'string' && (candidate.notificationMode === 'always' || candidate.notificationMode === 'hidden-only')) {
     result.notificationMode = candidate.notificationMode;
   }
+  if (typeof candidate.notifyOnSubtasks === 'boolean') {
+    result.notifyOnSubtasks = candidate.notifyOnSubtasks;
+  }
   if (
     typeof candidate.toolCallExpansion === 'string'
     && (candidate.toolCallExpansion === 'collapsed'