fix: add isConnected into fixture

Author: standujar

packages/server/src/__tests__/fixtures/socketio-client.fixture.ts

@@ -127,6 +127,13 @@ export class SocketIOClientFixture {
     return this.client;
   }
 
+  /**
+   * Check if the client is currently connected
+   */
+  isConnected(): boolean {
+    return this.client?.connected ?? false;
+  }
+
   /**
    * Join a channel
    */