fix(desktop): report and mute a Browser guest that attaches after its session is hidden

The off-screen hook only re-ran when hidden/parked changed, and a guest has
no webContents id until it attaches. A page whose session was parked between
mount and attach was never reported hidden to main (so mouse back/reload
could still target it) and never muted. The pane now feeds the guest's
dom-ready to the hook, which re-reports and re-mutes for the attached id.

apps/desktop/src/app/chat/right-rail/preview-guest-offscreen.ts

@@ -15,7 +15,7 @@
  */
 
 import { useStore } from '@nanostores/react'
-import { type RefObject, useEffect } from 'react'
+import { type RefObject, useCallback, useEffect, useState } from 'react'
 
 import { usePaneVisible } from '@/components/pane-shell/pane-visibility'
 import { $parkedTreePanes } from '@/components/pane-shell/tree/parked-panes'
@@ -55,10 +55,16 @@ function muteGuest(webview: OffscreenGuest): boolean {
   }
 }
 
-export function usePreviewGuestOffscreen(webviewRef: RefObject<null | OffscreenGuest>, tabId?: string): void {
+/** Reports and mutes the guest as it goes off screen. Returns a `dom-ready`
+ *  listener the pane must attach to its `<webview>`: a guest has no id until it
+ *  attaches, and one that attaches while its session is already hidden would
+ *  otherwise never be reported or muted (the effects only re-run on change). */
+export function usePreviewGuestOffscreen(webviewRef: RefObject<null | OffscreenGuest>, tabId?: string): () => void {
   const hidden = !usePaneVisible()
   const parkedPanes = useStore($parkedTreePanes)
   const parked = Boolean(tabId) && parkedPanes.has(`${PREVIEW_TILE_PREFIX}:${tabId}`)
+  const [attachedId, setAttachedId] = useState<null | number>(null)
+  const noteGuestReady = useCallback(() => setAttachedId(guestId(webviewRef.current)), [webviewRef])
 
   useEffect(() => {
     const id = guestId(webviewRef.current)
@@ -66,7 +72,7 @@ export function usePreviewGuestOffscreen(webviewRef: RefObject<null | OffscreenG
     if (id !== null) {
       window.hermesDesktop?.setPreviewGuestHidden?.(id, hidden)
     }
-  }, [hidden, webviewRef])
+  }, [attachedId, hidden, webviewRef])
 
   useEffect(() => {
     const webview = webviewRef.current
@@ -88,5 +94,7 @@ export function usePreviewGuestOffscreen(webviewRef: RefObject<null | OffscreenG
         // The guest went away while parked; nothing to restore.
       }
     }
-  }, [parked, webviewRef])
+  }, [attachedId, parked, webviewRef])
+
+  return noteGuestReady
 }

apps/desktop/src/app/chat/right-rail/preview-pane.test.tsx

@@ -945,6 +945,40 @@ describe('PreviewPane off-screen guest', () => {
     expect(setPreviewGuestHidden).toHaveBeenLastCalledWith(41, false)
   })
 
+  // A guest has no id until it attaches; one that attaches after its session
+  // was already parked must still be reported to main and muted.
+  it('reports and mutes a guest that attaches while its session is already hidden', async () => {
+    const setPreviewGuestHidden = vi.fn()
+    desktopWindow.hermesDesktop = { setPreviewGuestHidden } as unknown as Window['hermesDesktop']
+    act(() => setTreePaneParked('preview-tile:url:late', true))
+
+    let rendered!: ReturnType<typeof render>
+
+    await act(async () => {
+      rendered = render(
+        <PaneVisibleContext value={false}>
+          <PreviewPane tabId="url:late" target={target} />
+        </PaneVisibleContext>
+      )
+    })
+
+    let muted = false
+    const webview = rendered.container.querySelector('webview')!
+    Object.assign(webview, {
+      getWebContentsId: () => 52,
+      isAudioMuted: () => muted,
+      setAudioMuted: (next: boolean) => (muted = next)
+    })
+
+    await act(async () => {
+      webview.dispatchEvent(new Event('dom-ready'))
+    })
+
+    expect(setPreviewGuestHidden).toHaveBeenLastCalledWith(52, true)
+    expect(muted).toBe(true)
+    act(() => setTreePaneParked('preview-tile:url:late', false))
+  })
+
   // A hidden session's kept page keeps running, but is not heard from the chat
   // the user switched to; it comes back with the sound it had.
   async function renderAudibleGuest(tabId: string, mutedBefore: boolean) {

apps/desktop/src/app/chat/right-rail/preview-pane.tsx

@@ -276,7 +276,7 @@ export function PreviewPane({
   const lastRestartEventRef = useRef('')
   const previewContentRef = useRef<HTMLDivElement | null>(null)
   const webviewRef = useRef<PreviewWebview | null>(null)
-  usePreviewGuestOffscreen(webviewRef, tabId)
+  const noteGuestReady = usePreviewGuestOffscreen(webviewRef, tabId)
   const previewServerRestart = useStore($previewServerRestart)
   const consoleHeight = useStore(consoleState.$height)
   const consoleOpen = useStore(consoleState.$open)
@@ -1361,6 +1361,7 @@ export function PreviewPane({
     webview.addEventListener('page-title-updated', notePage)
     // #101880: never let a guest reach the native print panel.
     webview.addEventListener('dom-ready', armPrintGuard)
+    webview.addEventListener('dom-ready', noteGuestReady)
     host.appendChild(webview)
     webviewRef.current = webview
 
@@ -1378,10 +1379,11 @@ export function PreviewPane({
       webview.removeEventListener('did-stop-loading', onStop)
       webview.removeEventListener('page-title-updated', notePage)
       webview.removeEventListener('dom-ready', armPrintGuard)
+      webview.removeEventListener('dom-ready', noteGuestReady)
       webview.remove()
       setAnnotate(session => (session.mode ? { ...endAnnotateMode(session), stack: emptyAnnotateStack() } : session))
     }
-  }, [appendConsoleEntry, consoleState, copy, isRemoteHtml, isWebPreview, tabId, target.kind])
+  }, [appendConsoleEntry, consoleState, copy, isRemoteHtml, isWebPreview, noteGuestReady, tabId, target.kind])
 
   // Steers the LIVE guest when the session opens a new URL (#120265): loadURL
   // keeps the webview instance (JS state, cookies, form data, scroll, refs,