fix(mobile): clean up sockets when simulation starts

When the server URL is cleared, close the active WebSocket and cancel pending reconnects so simulation mode does not race with stale network state.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

ui/mobile/src/__tests__/services/ws.service.test.ts

@@ -109,6 +109,62 @@ describe('WsService', () => {
       expect(ws.getStatus()).toBe('simulated');
       ws.disconnect();
     });
+
+    it('cleans up active sockets and pending reconnects when switching to simulation mode', () => {
+      const sockets: MockWebSocketInstance[] = [];
+      const OrigWebSocket = globalThis.WebSocket;
+
+      class MockWebSocket {
+        static OPEN = 1;
+        static CONNECTING = 0;
+        static CLOSED = 3;
+        readyState = MockWebSocket.OPEN;
+        onopen: (() => void) | null = null;
+        onclose: ((event: { code: number }) => void) | null = null;
+        onerror: (() => void) | null = null;
+        onmessage: (() => void) | null = null;
+        close = jest.fn((code?: number) => {
+          this.readyState = MockWebSocket.CLOSED;
+          this.onclose?.({ code: code ?? 1000 });
+        });
+
+        constructor(_url: string) {
+          sockets.push(this as unknown as MockWebSocketInstance);
+        }
+      }
+
+      type MockWebSocketInstance = {
+        onclose: ((event: { code: number }) => void) | null;
+        close: jest.Mock;
+      };
+
+      globalThis.WebSocket = MockWebSocket as any;
+
+      try {
+        const ws = createWsService();
+        ws.connect('http://localhost:3000');
+        expect(sockets).toHaveLength(1);
+
+        ws.connect('');
+        expect(sockets[0].close).toHaveBeenCalledWith(1000, 'switch to simulation');
+        expect(ws.getStatus()).toBe('simulated');
+        ws.disconnect();
+
+        const wsWithReconnect = createWsService();
+        wsWithReconnect.connect('http://localhost:3000');
+        expect(sockets).toHaveLength(2);
+
+        sockets[1].onclose?.({ code: 1006 });
+        wsWithReconnect.connect('');
+
+        jest.advanceTimersByTime(60_000);
+        expect(sockets).toHaveLength(2);
+        expect(wsWithReconnect.getStatus()).toBe('simulated');
+        wsWithReconnect.disconnect();
+      } finally {
+        globalThis.WebSocket = OrigWebSocket;
+      }
+    });
   });
 
   describe('subscribe and unsubscribe', () => {

ui/mobile/src/services/ws.service.ts

@@ -22,6 +22,13 @@ class WsService {
     this.reconnectAttempt = 0;
 
     if (!url) {
+      this.clearReconnectTimer();
+      if (this.ws) {
+        const socket = this.ws;
+        this.ws = null;
+        socket.onclose = null;
+        socket.close(1000, 'switch to simulation');
+      }
       this.handleStatusChange('simulated');
       this.startSimulation();
       return;