fix: suppress notification spam on app re-open (#623)

* fix: suppress notification spam on app re-open

- Add background_task notification category (default ON) so users can
  toggle off background-task pings via Settings → Notifications
- Route notify-user builtin through notifyIfEnabled gate so the
  category toggle takes effect
- Add 60s startup grace period: background-task notifications fired
  within 60s of launch are suppressed, killing the reopen flood where
  all queued agents complete at once
- Suppress new_email notifications for emails older than 5 min so
  Gmail's startup backlog replay doesn't surface day-old mail

Fixes both issues reported by Ramnique.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: skip automatic chat_completion ping for background task agents

Background task runs were triggering "Response ready / Your agent
finished responding" on every completion. Skip the automatic
chat_completion notification when finalState.runUseCase ===
'background_task_agent' — background tasks notify explicitly via
notify-user when they have something worth surfacing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: correct notification deeplinks and skip internal agent pings

- runtime.ts: also skip chat_completion ping for knowledge_sync
  useCase (agent_notes_agent was opening notes view on click)
- sync_gmail.ts: new_email notification now links to specific
  email thread (rowboat://open?type=email&threadId=...)
- App.tsx: add email case to parseDeepLink, parse threadId param,
  wire threadId through applyViewState, update viewStatesEqual

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: distinguish background-agent notifications from auto knowledge-sync

Per team clarification, two background types are handled differently:
- knowledge_sync (auto knowledge-graph generation): never notifies;
  skips the generic chat_completion ping entirely.
- background_task_agent (user-configured agents): notifies via its
  own notify-user path, gated behind the toggleable "Background
  agents" category, deep-linking to the background-tasks page.

- runtime.ts: skip the generic chat_completion completion ping for
  both knowledge_sync and background_task_agent (the latter notifies
  via notify-user, so the generic ping would duplicate it).
- builtin-tools.ts: notify-user branches on getCurrentUseCase() —
  background agents route through notifyIfEnabled('background_task')
  with a bg-tasks deeplink default; chat agents notify directly.
- App.tsx: add the bg-tasks deeplink target (ViewState, parseDeepLink,
  applyViewState, currentViewState).
- settings-dialog.tsx: rename the category label to "Background agents".
- runner.ts: wrap the background-task run in withUseCase so tools see
  the correct use-case context.

* fix: route coding-session notifications through notifyIfEnabled

Code-mode status-tracker was calling notificationService.notify() directly,
bypassing the user's notification-category toggles. Routed both calls
through notifyIfEnabled() with correct categories:
- needs-you state → agent_permission
- idle after 30s  → chat_completion

Removed now-redundant container/INotificationService plumbing.

* fix: fall back to persisted run useCase when ALS context is missing in notify-user

AsyncLocalStorage does not propagate across the background-task agent's
async generator — getCurrentUseCase() returns undefined inside notify-user,
causing the background_task_agent branch to be skipped and the Background
agents toggle to be ignored.

Fix: load persisted useCase from run record via fetchRun(ctx.runId) when
ALS is falsy. Lazy dynamic import() avoids the known module-init cycle.
Background-agent notifications now correctly respect the toggle and only
fire when the app is in the background, with deep link to the bg-tasks page.

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

apps/x/packages/shared/src/notification-settings.ts

@@ -6,17 +6,20 @@ import { z } from 'zod';
  * - chat_completion:  an agent finished generating a response
  * - new_email:        a new email arrived during incremental Gmail sync
  * - agent_permission: an agent is requesting permission to run a tool
+ * - background_task:  a background task agent pinged via the notify-user tool
  */
 export const NotificationCategorySchema = z.enum([
   'chat_completion',
   'new_email',
   'agent_permission',
+  'background_task',
 ]);
 
 export const NotificationCategoriesSchema = z.object({
   chat_completion: z.boolean(),
   new_email: z.boolean(),
   agent_permission: z.boolean(),
+  background_task: z.boolean(),
 });
 
 export const NotificationSettingsSchema = z.object({
@@ -28,6 +31,7 @@ export const DEFAULT_NOTIFICATION_SETTINGS: NotificationSettings = {
     chat_completion: true,
     new_email: true,
     agent_permission: true,
+    background_task: true,
   },
 };