Fix detached-window IPC scoping and pane-transfer session loss

- capabilities/default.json: extend window scope to "pane-window-*" so
  detached windows can invoke/listen (fixes blank panes B2-B5).
- App.tsx: memoize the destructive take_pending_window_init read at module
  scope so React StrictMode's double mount-effect doesn't consume the
  transfer payload twice and lose the adopted PTY session.
- lib.rs: add `use tauri::Manager;` for Window::app_handle() in on_window_event.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/App.tsx

@@ -42,6 +42,22 @@ const MAIN_WINDOW_LABEL = "main";
  *  this window's state to the cross-window aggregator. */
 const CURRENT_WINDOW_LABEL = getCurrentWebviewWindow().label;
 const IS_MAIN_WINDOW = CURRENT_WINDOW_LABEL === MAIN_WINDOW_LABEL;
+
+/** `take_pending_window_init` is a DESTRUCTIVE backend read (it removes the
+ *  entry). React StrictMode runs the mount effect twice in dev, so a plain
+ *  call would consume the payload on the first (cancelled) pass and hand the
+ *  second pass `null` — booting a fresh "Default" workspace and spawning a new
+ *  PTY instead of adopting the transferred one (session lost). Memoize the
+ *  promise at module scope so the backend take happens exactly once per window
+ *  and every effect pass awaits the same result. */
+let pendingInitOnce: Promise<Awaited<ReturnType<typeof takePendingWindowInit>>> | null =
+  null;
+const consumePendingWindowInit = () => {
+  if (!pendingInitOnce) {
+    pendingInitOnce = takePendingWindowInit(CURRENT_WINDOW_LABEL);
+  }
+  return pendingInitOnce;
+};
 import {
   type TreeNode,
   type NodeId,
@@ -263,7 +279,7 @@ export default function App() {
 
       if (!IS_MAIN_WINDOW) {
         try {
-          const pending = await takePendingWindowInit(CURRENT_WINDOW_LABEL);
+          const pending = await consumePendingWindowInit();
           if (pending) {
             try {
               const adoptedLeaf = JSON.parse(pending.leafJson) as LeafNode;