Add bot-driven room app UI via im.paarrot.ui state.

Bots can publish a declarative panel UI that takes over a room; user
actions are sent as im.paarrot.ui.action timeline events.

src/app/features/room/RoomTimeline.tsx

@@ -2011,6 +2011,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
         return 'CALL_EVENT_PENDING' as unknown as React.ReactNode;
       },
       [MessageEvent.RelayEmojiConfetti]: () => null,
+      [MessageEvent.PaarrotUiAction]: () => null,
     },
     (mEventId, mEvent, item) => {
       if (!showHiddenEvents) return null;