feat: media player API, web player panel, and Hope music MCP

- web/media_server.py: FastAPI service owning the permanent library
  (library.json + ./media volume), yt-dlp YouTube Music search, queued
  download jobs with mp3 transcode (ffmpeg), per-room player desired
  state, and an HTTPS proxy for external live-stream URLs.
- agent/media_mcp.py: Hope tools — search_music, play_song,
  offer_song_choices, pause/resume/stop/skip/seek, now_playing,
  list_library, add_stream.
- agent/agent.py: media toolset wiring + conversation rule (music
  playing disables the agent mic; re-engaging pauses music).
- web UI: slide-out Music panel (search, suggestions, library, live
  stream add, play/pause, ±10s, seek, volume) with a reconciling poller
  and media_state data-channel reports.
- token server returns the minted room name; nginx serves /media/files
  as static (native Range) and proxies /media/api to the media server.
- supervisord runs media-server; compose mounts ./media and adds
  ffmpeg to the image.

web/token_server.py

@@ -97,6 +97,9 @@ class Handler(BaseHTTPRequestHandler):
         resp = json.dumps(
             {
                 "token": token,
+                # The room name scopes media-server player state; the UI sends
+                # it with every /media/api/ call.
+                "room": room_name,
                 "user": {
                     "id": user_id,
                     "display_name": profile.get("display_name") or user_id,