Phase 3.2 docs + Phase 3.1 testing fixes

- Add phase3.2.md requirement: overlay UX, mitra activity log
- Add phase3.2-plan.md implementation plan
- Fix stale request validation: add GET /:sessionId/status endpoint
- Fix notification tap flow: setIncomingFromNotification + onChatRequestTapped
- IncomingRequestSheet shows stale message instead of auto-dismiss
- Home screen validates on resume, shows immediately on fresh WS

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mitra_app/lib/features/home/home_screen.dart

@@ -68,16 +68,10 @@ class _HomeScreenState extends ConsumerState<HomeScreen> with WidgetsBindingObse
       }
     });
 
-    // Listen for incoming chat requests
+    // Listen for incoming chat requests — fresh from WS, show immediately
     ref.listen(chatRequestProvider, (prev, next) {
       if (next is ChatRequestIncomingData) {
-        // Validate request is still pending before showing sheet
-        ref.read(chatRequestProvider.notifier).validateIncomingRequest().then((_) {
-          final current = ref.read(chatRequestProvider);
-          if (current is ChatRequestIncomingData) {
-            _showIncomingRequest(current.sessionId);
-          }
-        });
+        _showIncomingRequest(next.sessionId);
       } else if (next is ChatRequestAcceptedData) {
         final session = next.session;
         final sessionId = session['session_id'] as String? ?? session['id'] as String;