refactor(ui): fold the sidebar overlay exemption into the selector

Match the existing self-exclusion convention used by useWorkspaceBoardPanel
and AgentDashboardDrawer instead of a separate matches() guard, and drop the
non-null assertion from the test.

No behavior change.

src/renderer/src/lib/visible-overlay.test.ts

@@ -35,7 +35,7 @@ describe('hasVisibleOverlay', () => {
 
     expect(hasVisibleOverlay()).toBe(false)
 
-    document.querySelector('[data-worktree-sidebar]')!.innerHTML = '<div role="menu"></div>'
+    mount('<div role="listbox" data-worktree-sidebar><div role="menu"></div></div>')
 
     expect(hasVisibleOverlay()).toBe(true)
   })

src/renderer/src/lib/visible-overlay.ts

@@ -1,4 +1,6 @@
-const OVERLAY_SELECTOR = '[role="dialog"], [role="alertdialog"], [role="listbox"], [role="menu"]'
+// The always-mounted worktree sidebar is page chrome, not an Escape-owning popup.
+const OVERLAY_SELECTOR =
+  '[role="dialog"], [role="alertdialog"], [role="listbox"]:not([data-worktree-sidebar]), [role="menu"]'
 
 type VisibleOverlayOptions = {
   /** Overlays inside a match are treated as page content, not as a layer above it. */
@@ -15,10 +17,6 @@ export function hasVisibleOverlay(options?: VisibleOverlayOptions): boolean {
     if (!(element instanceof HTMLElement)) {
       return false
     }
-    // The persistent workspace list is page chrome, not an Escape-owning popup.
-    if (element.matches('[role="listbox"][data-worktree-sidebar]')) {
-      return false
-    }
     if (element.closest('[aria-hidden="true"]')) {
       return false
     }