🐛(frontend) fix joined notification tile no longer rendering properly

The toast is enqueued on `ParticipantConnected`, which livekit-client
fires before the participant's track publications exist. At that
point `getTrackPublication(Camera)` is `undefined`, and the track
ref used by the toast is frozen that way — the toast never
re-subscribes to the participant.

Downstream effects:

* LiveKit's `useIsMuted` initializes to `false` when there is no
  publication, so the tile first paints with
  `data-lk-video-muted="false"`, which the stock CSS maps to
  placeholder `opacity: 0` — a blank box.
* Its effect then subscribes to `mutedObserver`, which defaults to
  `true` for the same situation, triggering a second render and
  only then starting the 200 ms fade-in. That render-effect-render
  transition is the visible lag behind the text.
* Because the track ref never updates, no `VideoTrack` ever mounts.
  When the camera is later subscribed, the placeholder fades out
  again, leaving the tile empty.

Re-derive the track ref inside the toast when the participant's
publications become available, so `useIsMuted` sees the real state
from the start and the tile renders the video (or a stable
placeholder) instead of a blank box.

CHANGELOG.md

@@ -30,6 +30,7 @@ and this project adheres to
 - 🐛(frontend) use state instead of a ref for MoreControls container
 - 🐛(frontend) stop init_virtual_background from firing on blur updates
 - 🐛(frontend) hoist mute confirmation dialog to VideoConference level
+- 🐛(frontend) fix joined notification tile no longer rendering properly
 
 ## [1.27.0] - 2026-08-14
 

src/frontend/src/features/notifications/components/ToastJoined.tsx

@@ -1,5 +1,5 @@
 import { useToast } from 'react-aria'
-import { useRef } from 'react'
+import { useMemo, useRef } from 'react'
 import { Button as RACButton } from 'react-aria-components'
 import { Track } from 'livekit-client'
 import Source = Track.Source
@@ -11,6 +11,7 @@ import { Div } from '@/primitives'
 import { useTranslation } from 'react-i18next'
 import { StyledToastContainer } from './StyledToastContainer'
 import { setPinnedTrack } from '@/stores/layout'
+import { useParticipantTracks } from '@livekit/components-react'
 
 const ClickableToast = styled(RACButton, {
   base: {
@@ -30,13 +31,17 @@ export function ToastJoined({ state, ...props }: Readonly<ToastProps>) {
   )
   const participant = props.toast.content.participant
 
-  if (!participant) return
+  const [cameraTrack] = useParticipantTracks(
+    [Source.Camera],
+    participant?.identity
+  )
 
-  const trackReference = {
-    participant,
-    publication: participant.getTrackPublication(Source.Camera),
-    source: Source.Camera,
-  }
+  const trackReference = useMemo(
+    () => cameraTrack ?? { participant, source: Source.Camera },
+    [cameraTrack, participant]
+  )
+
+  if (!participant) return
 
   return (
     <StyledToastContainer {...toastProps} ref={ref}>