Support app.relay.emoji_confetti on jumbo emoji clicks with canvas physics,
per-emoji particle profiles, and a fixed overlay that does not affect scroll.
Also add a Vite playground for live component previews and theme hover preview.
- Enhance RoomInput to support sending messages as replies in threads by adding `threadRootId` prop.
- Update RoomTimeline to manage active thread state and handle opening threads.
- Implement ThreadView component to display thread messages and input.
- Create HomeThreadsCategory to list threads user has participated in.
- Introduce activeThreadIdAtomFamily to manage active thread state across rooms.
