fix(overlay): prevent layout picker double-trigger on rapid shortcut press

Replace toggle guard with simple existence guard so the shortcut only
shows the picker if no window exists, preventing deleteLater() races
and stale KeyboardInteractivityExclusive grabs on Wayland.

Co-Authored-By: claude-flow <ruv@ruv.net>

Author: fuddlesworth

src/daemon/overlayservice.cpp

@@ -3065,9 +3065,10 @@ void OverlayService::onSnapAssistWindowSelected(const QString& windowId, const Q
 
 void OverlayService::showLayoutPicker(const QString& screenName)
 {
-    // Toggle: if already visible, dismiss instead of recreating
-    if (isLayoutPickerVisible()) {
-        hideLayoutPicker();
+    // Guard: if picker window already exists (visible or being set up), do nothing.
+    // Prevents double-trigger when shortcut fires before KeyboardInteractivityExclusive
+    // grabs the keyboard on Wayland, and avoids deleteLater() races with stale grabs.
+    if (m_layoutPickerWindow) {
         return;
     }