fix(autofill): refuse a fill while a blocking operation runs

Guarded in autofillHandleRequest, upstream of the single-match versus picker split, so it covers Ctrl+Shift+L/P/T and both outcomes: the picker would open behind the overlay, and a single-match fill would minimise our window mid-operation. Cancels the request so Delphi drops the captured target HWND.

js/app.autofill.js

@@ -236,6 +236,17 @@ function autofillReportResult(ok) {
 async function autofillHandleRequest(windowTitle, kind) {
     if (!state.autofillEnabled) return;
 
+    // A blocking operation owns the screen (export, sync, rotation). Covers all
+    // three hotkeys and both outcomes: the multi-match picker would open behind
+    // the overlay, unreachable, and a single-match fill would minimise our
+    // window and hand the foreground away mid-operation. cancelAutofill so
+    // Delphi doesn't keep the captured target HWND for a fill that never comes.
+    if (typeof isBusy === 'function' && isBusy()) {
+        Bridge.cancelAutofill();
+        toast('Busy — try again in a moment', 'warning');
+        return;
+    }
+
     if (!state.cryptoKey || state.locked || !state.token) {
         // Vault is locked — bring the app to the front so the user can
         // unlock immediately, rather than silently no-op'ing the hotkey.