refactor(desktop): generalize focus check to isFocusWithin primitive

Replace the one-off isTerminalFocused with isFocusWithin(selector) in the
keybinds lib (beside isEditableTarget) — the reusable primitive for any
focus-scoped shortcut. The terminal marks itself data-terminal and the ⌘W
handler routes via isFocusWithin('[data-terminal]'); future surfaces just add
their own marker.

apps/desktop/src/app/desktop-controller.tsx

@@ -10,6 +10,7 @@ import { GatewayConnectingOverlay } from '@/components/gateway-connecting-overla
 import { Pane, PaneMain } from '@/components/pane-shell'
 import { RemoteDisplayBanner } from '@/components/remote-display-banner'
 import { useMediaQuery } from '@/hooks/use-media-query'
+import { isFocusWithin } from '@/lib/keybinds/combo'
 import { cn } from '@/lib/utils'
 import { useSkinCommand } from '@/themes/use-skin-command'
 
@@ -129,7 +130,7 @@ import { ReviewPane } from './right-sidebar/review'
 import { $terminalTakeover } from './right-sidebar/store'
 import { TerminalPaneChrome } from './right-sidebar/terminal/chrome'
 import { PersistentTerminal } from './right-sidebar/terminal/persistent'
-import { closeActiveTerminal, isTerminalFocused } from './right-sidebar/terminal/terminals'
+import { closeActiveTerminal } from './right-sidebar/terminal/terminals'
 import { CRON_ROUTE, NEW_CHAT_ROUTE, routeSessionId, sessionRoute, SETTINGS_ROUTE } from './routes'
 import { SessionPickerOverlay } from './session-picker-overlay'
 import { SessionSwitcher } from './session-switcher'
@@ -397,7 +398,7 @@ export function DesktopController() {
       // Terminal focused: ⌘W closes the active terminal. Ctrl+W is left untouched
       // for the shell's werase, and nothing else may steal ⌘/Ctrl+W from a
       // focused terminal (so it never closes a preview tab out from under it).
-      if (isTerminalFocused()) {
+      if (isFocusWithin('[data-terminal]')) {
         if (event.metaKey && !event.ctrlKey) {
           event.preventDefault()
           event.stopPropagation()

apps/desktop/src/app/right-sidebar/terminal/instance.tsx

@@ -40,6 +40,8 @@ export function TerminalInstance({ id, active, cwd, onAddSelectionToChat }: Term
         'absolute inset-0 flex flex-col bg-(--ui-editor-surface-background) px-2 pb-2 pt-0',
         active ? 'visible' : 'invisible pointer-events-none'
       )}
+      // Focus-scope marker so isFocusWithin('[data-terminal]') can route ⌘W here.
+      data-terminal=""
     >
       {status === 'starting' && (
         <div className="pointer-events-none absolute inset-0 z-10 grid place-items-center">

apps/desktop/src/app/right-sidebar/terminal/terminals.ts

@@ -95,12 +95,6 @@ export function closeActiveTerminal(): void {
   }
 }
 
-/** True while an in-app terminal's xterm holds focus (its helper textarea is the
- *  active element) — lets ⌘W close the focused terminal without a ref dance. */
-export function isTerminalFocused(): boolean {
-  return document.activeElement?.classList.contains('xterm-helper-textarea') ?? false
-}
-
 export function closeOtherTerminals(id: string): void {
   const keep = $terminals.get().find(term => term.id === id)
 

apps/desktop/src/lib/keybinds/combo.ts

@@ -175,6 +175,13 @@ export function formatCombo(combo: string): string {
   return IS_MAC ? tokens.join('') : tokens.join('+')
 }
 
+// True when focus currently sits inside an element matching `selector`. The
+// primitive for focus-scoped shortcuts — e.g. routing ⌘W to whichever surface
+// (terminal, preview, …) owns focus.
+export function isFocusWithin(selector: string): boolean {
+  return document.activeElement?.closest(selector) != null
+}
+
 // True when focus is in a text-entry surface, so bare-key shortcuts don't fire
 // while the user is typing.
 export function isEditableTarget(target: EventTarget | null): boolean {