fix(hotkeys): block the editor and quick search while a blocking operation runs

Global hotkeys come from Win32, outside the window, so the busy overlay intercepts nothing: Ctrl+Shift+A opened the editor behind it, unreachable. Guarded in openSlideOver and openQuickSearchModal rather than at each trigger - every caller routes through them, and no save path raises the overlay.

js/app.overlays.js

@@ -465,6 +465,13 @@ function endTour() {
 }
 
 function openQuickSearchModal(hideAfter, forFill) {
+    // Same reason as the editor: the hotkey fires from outside the window, so
+    // the busy overlay covering the app stops nothing — the modal would open
+    // behind it, unreachable.
+    if (typeof isBusy === 'function' && isBusy()) {
+        toast('Busy — try again in a moment', 'warning');
+        return;
+    }
     const modal = document.getElementById('quickSearchModal');
     const input = document.getElementById('quickSearchInput');
     modal.classList.remove('is-hidden');