feat(session-status): mobile session quick switch with running/unread indicators (#340)

* feat(session-status): implement server-authoritative session status tracking

- Add server-side session states and attention tracking with Map storage
- Implement SSE event broadcasting (openchamber:session-status)
- Add REST API endpoints for status/attention queries
- Replace client-side polling with HTTP polling + SSE push
- Track needsAttention based on user message + completion + unviewed
- Add MobileSessionStatusBar for mobile UI
- Handle session view/unview/message-sent state transitions
- Add 24h cleanup for old session states

* feat(session-status): add unread indicator to mobile session status bar

* refactor(session-status): extract SessionStatusHeader component

Extract the session status header into a reusable component and improve
layout structure in CollapsedView and ExpandedView.

* feat(session-status): optimize mobile session status bar UI

* refactor(session-status): remove interval polling, use snapshot sync on reconnect/visibility

- unifies session status/attention sync with existing SSE lifecycle, fixes no-op store churn bug, and drops duplicated client activity state while preserving mobile unread/running UX.

---------

Co-authored-by: Jovines <jovines@qq.com>
Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/App.tsx

@@ -10,6 +10,7 @@ import { useEventStream } from '@/hooks/useEventStream';
 import { useKeyboardShortcuts } from '@/hooks/useKeyboardShortcuts';
 import { useMenuActions } from '@/hooks/useMenuActions';
 import { useSessionStatusBootstrap } from '@/hooks/useSessionStatusBootstrap';
+import { useServerSessionStatus } from '@/hooks/useServerSessionStatus';
 import { useSessionAutoCleanup } from '@/hooks/useSessionAutoCleanup';
 import { useRouter } from '@/hooks/useRouter';
 import { usePushVisibilityBeacon } from '@/hooks/usePushVisibilityBeacon';
@@ -158,6 +159,10 @@ function App({ apis }: AppProps) {
 
   useEventStream();
 
+  // Server-authoritative session status polling
+  // Replaces SSE-dependent status updates with reliable HTTP polling
+  useServerSessionStatus();
+
   usePushVisibilityBeacon();
 
   useRouter();