fix(maestro): reconnect attach/structured sockets on Android resume

The visibility recovery only reconnected the catalog and daemon-link
sockets. Per-pane attach and structured WebSockets relied on backoff
timers that Android suspends alongside the sockets, leaving the
terminal disconnected after backgrounding.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/components/structured/useStructuredSession.ts

@@ -196,12 +196,24 @@ export function useStructuredSession(
       connect();
     };
 
+    // Mobile browsers suspend timers and silently kill WebSockets in the
+    // background. Kick a fresh connect when the page becomes visible again.
+    const onVisibility = () => {
+      if (document.visibilityState !== "visible" || disposed) return;
+      if (socket && (socket.readyState === WebSocket.OPEN || socket.readyState === WebSocket.CONNECTING)) return;
+      cancelTimer();
+      setStatus("reconnecting");
+      connect();
+    };
+    document.addEventListener("visibilitychange", onVisibility);
+
     setStatus("connecting");
     connect();
 
     return () => {
       disposed = true;
       reconnectRef.current = () => {};
+      document.removeEventListener("visibilitychange", onVisibility);
       cancelTimer();
       closeSocket();
     };