fix(maestro): force-replace pane sockets on mobile resume

Mobile browsers report readyState === OPEN after background suspension
even though the OS killed the TCP connection. The per-pane visibility
handlers skipped reconnection in that case, leaving the pane frozen
until TCP keepalive fired (30–120 s on cellular).

Remove the readyState guard and unconditionally replace the socket on
visibility return — same pattern the events socket already uses. Also
let pageshow/online fire recovery without the visibilityState gate,
since some mobile browsers fire pageshow before updating that property.

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

web/src/App.tsx

@@ -113,15 +113,23 @@ function Shell() {
   // a transient lost connection has already recovered.
   useEffect(() => {
     const recover = () => {
-      if (document.visibilityState !== "visible") return;
       void linkStore.getState().probe();
       catalogStore.getState().reconnect();
     };
-    document.addEventListener("visibilitychange", recover);
+    // visibilitychange fires reliably on tab/app switch; guard it so we don't
+    // probe while the page is being hidden.
+    const onVisibility = () => {
+      if (document.visibilityState !== "visible") return;
+      recover();
+    };
+    // pageshow (bfcache restore) and online (network back) indicate the page
+    // is active — fire unconditionally since visibilityState may lag behind on
+    // some mobile browsers.
+    document.addEventListener("visibilitychange", onVisibility);
     window.addEventListener("pageshow", recover);
     window.addEventListener("online", recover);
     return () => {
-      document.removeEventListener("visibilitychange", recover);
+      document.removeEventListener("visibilitychange", onVisibility);
       window.removeEventListener("pageshow", recover);
       window.removeEventListener("online", recover);
     };

web/src/components/structured/useStructuredSession.ts

@@ -197,11 +197,12 @@ export function useStructuredSession(
     };
 
     // Mobile browsers suspend timers and silently kill WebSockets in the
-    // background. Kick a fresh connect when the page becomes visible again.
+    // background. The browser often still reports readyState === OPEN because
+    // TCP keepalive hasn't noticed the dead connection yet. Force-replace
+    // unconditionally — connect() closes the old socket first, and the server
+    // replays the full transcript on every reconnect so nothing is lost.
     const onVisibility = () => {
       if (document.visibilityState !== "visible" || disposed) return;
-      if (socket && (socket.readyState === WebSocket.OPEN || socket.readyState === WebSocket.CONNECTING)) return;
-      cancelTimer();
       setStatus("reconnecting");
       connect();
     };

web/src/components/terminal/TerminalPane.tsx

@@ -303,17 +303,22 @@ export const TerminalPane = forwardRef<TerminalPaneHandle, TerminalPaneProps>(
       ta?.addEventListener("blur", onTaBlur);
 
       // Mobile browsers (Android especially) suspend timers and silently kill
-      // WebSockets when the app goes to background. The backoff timer set by
-      // onclose is frozen too, so recovery stalls until visibility returns. Kick
-      // a fresh connect immediately when the page becomes visible again.
+      // WebSockets when the app goes to background. The browser often still
+      // reports readyState === OPEN because TCP keepalive hasn't noticed the
+      // dead connection yet. Force-replace the socket unconditionally —
+      // a genuinely alive server socket gets a clean close, and the reconnect
+      // replays the scrollback so nothing is lost.
       const onVisibility = () => {
         if (document.visibilityState !== "visible" || disposed) return;
-        if (ws.readyState === WebSocket.OPEN || ws.readyState === WebSocket.CONNECTING) return;
-        // Cancel any pending backoff — we're reconnecting right now.
         if (reconnectTimer !== null) {
           window.clearTimeout(reconnectTimer);
           reconnectTimer = null;
         }
+        // Detach the old socket's handlers so its close event doesn't race
+        // with the fresh connection (same pattern as catalogStore.reconnect).
+        ws.onclose = null;
+        ws.onerror = null;
+        ws.close();
         reconnectMs = INITIAL_RECONNECT_MS;
         onStatusChange?.("reconnecting");
         connect();