feat(node): Music app node-side — indexing, MusicBrainz enrichment, protocol

Implements the node half of docs/musicbay.md against MNP 0.8:

- IndexEntry gains artist/album/track_no (reuses duration/thumb_hash/
  display_title, already generic). New musicbrainz_config/_enabled and
  music_meta_req/_resp message pairs, mirroring the TMDB shape.
- title_parse.parse_track_filename: track-number-prefix + title parsing,
  fallback-only (embedded tags are the primary source, unlike Videos).
- indexer.enrich_audio.AudioEnricher: mutagen-based tag/embedded-cover
  extraction through its own bounded pool (asyncio.to_thread, no
  subprocess — no ffmpeg-shaped deadlock risk). Gated on "music" in a
  group's enabled_apps rather than a video_root-style scoped folder.
- musicbrainz.py: MusicBrainzClient — no API key (unlike TMDB), just a
  self-imposed ~1 req/s pace and a configurable, non-default User-Agent
  contact string; inert (no calls at all) when no contact is configured,
  never sends an unidentified client.
- media_cache.py: file_mbid/mbid_meta tables alongside the existing TMDB
  ones, cover art reusing the thumbs table via a synthetic
  musicbrainz:{mbid} id, pruned on file deletion.
- roster.py/ops.py/webrtc_server.py: musicbrainz_contact (node-wide) and
  musicbrainz_enabled (per-group, from the start) as signed operator
  settings, ALLOWED_APPS gains "music", _do_music_meta_request resolves
  and caches a release-level MusicBrainz match per (artist, album).
- daemon.py: AudioEnricher/MusicBrainzClient wired alongside the video
  ones; a group's existing library is swept when "music" is newly
  enabled (no video_root equivalent — see musicbay.md §2.1).

41 new tests (musicbrainz.py against a mocked transport, admin-op policy
for both new settings, media_cache round-trip/pruning, enrich_audio
end-to-end against real ffmpeg-generated MP3s). Full suite (common +
node + hub): 1116 passed, no regressions.

Client-side (music-app.js, persistent player bar) not started yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KBi7ALLGfwcjBXt57yNMcy

1 files changed, 42 insertions, 0 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/ops.py b/packages/meshbay-node/src/meshbay_node/ops.py
index a232ba2..d439ec3 100644
--- a/packages/meshbay-node/src/meshbay_node/ops.py
+++ b/packages/meshbay-node/src/meshbay_node/ops.py
@@ -728,6 +728,14 @@ async def set_enabled_apps(state: dict, group_id: str, apps: list[str]) -> dict:
                                   set_by=state.get("node_user_id", ""))
     ctx["enabled_apps"] = apps
     log.info("Enabled apps for group %s: %s", group_id[:8], ",".join(sorted(apps)))
+    if "music" in apps:
+        # Music has no root of its own to key a sweep off (unlike
+        # set_video_root's enrich_video_root_fn) — turning the app on at all
+        # is the trigger, mirroring that same "sweep what's already there"
+        # need (docs/musicbay.md §2.1, daemon._enrich_music_now).
+        enrich_fn = state.get("enrich_music_now_fn")
+        if enrich_fn:
+            asyncio.ensure_future(enrich_fn(group_id))
     return {"apps": apps, "group_id": group_id}
 
 
@@ -781,6 +789,40 @@ async def set_tmdb_enabled(state: dict, group_id: str, enabled: bool) -> dict:
     return {"enabled": enabled, "group_id": group_id}
 
 
+# ── MusicBrainz config (Music app) ───────────────────────────────────────────
+
+async def set_musicbrainz_config(state: dict, contact: str | None = None) -> dict:
+    """
+    The node-wide User-Agent contact string MusicBrainz's usage policy asks
+    for (docs/musicbay.md §3.2). Unlike set_tmdb_config there is no token to
+    manage — MusicBrainz's read endpoints need no credential — so this is a
+    single field. `contact=""` explicitly clears a previously-set contact
+    (reverting to "no calls at all", never a generic/unidentified
+    User-Agent); `contact=None` leaves whatever was there unchanged.
+    """
+    roster = _roster(state)
+    await roster.set_musicbrainz_contact(contact, set_by=state.get("node_user_id", ""))
+    if contact is not None:
+        state["musicbrainz_contact_configured"] = bool(contact)
+    log.info("MusicBrainz config: contact_configured=%s", bool(contact))
+    return {"contact_configured": state.get("musicbrainz_contact_configured", False)}
+
+
+async def set_musicbrainz_enabled(state: dict, group_id: str, enabled: bool) -> dict:
+    """
+    Whether MusicBrainz lookups run for this group at all
+    (docs/musicbay.md §6) — per-group from the start, same reasoning as
+    set_tmdb_enabled: a real media-library group and a test/demo group on
+    one node need not share the decision to make outbound requests.
+    """
+    roster = _roster(state)
+    ctx = _group_ctx(state, group_id)
+    await roster.set_musicbrainz_enabled(group_id, enabled, set_by=state.get("node_user_id", ""))
+    ctx["musicbrainz_enabled"] = enabled
+    log.info("MusicBrainz enabled for group %s: %s", group_id[:8], enabled)
+    return {"enabled": enabled, "group_id": group_id}
+
+
 async def set_video_root(state: dict, group_id: str, path: str) -> dict:
     """
     Which folder (possibly a subfolder of a shared root) is the Videos app's