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/core/chat/chat_request_notifier.dart

@@ -130,19 +130,26 @@ class ChatRequest extends _$ChatRequest {
     }
   }
 
+  /// Called when user taps a chat_request notification. Sets the incoming state
+  /// with the given session and validates it's still pending.
+  Future<void> setIncomingFromNotification(String sessionId) async {
+    state = ChatRequestIncomingData(sessionId);
+    await validateIncomingRequest();
+  }
+
   /// Check if the current incoming request is still valid (pending_acceptance).
   /// If stale, reset to listening state.
   Future<void> validateIncomingRequest() async {
     if (state is! ChatRequestIncomingData) return;
     final sessionId = (state as ChatRequestIncomingData).sessionId;
     try {
-      final response = await _apiClient.get('/api/shared/chat/$sessionId/info');
+      final response = await _apiClient.get('/api/mitra/chat-requests/$sessionId/status');
       final status = response['data']?['status'] as String?;
       if (status != 'pending_acceptance') {
         state = const ChatRequestListeningData();
       }
     } catch (_) {
-      state = const ChatRequestListeningData();
+      // On error, keep current state — don't dismiss valid requests
     }
   }