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, 51 insertions, 2 deletions

diff --git a/packages/meshbay-node/tests/test_media_cache.py b/packages/meshbay-node/tests/test_media_cache.py
index b66c448..e70ef43 100644
--- a/packages/meshbay-node/tests/test_media_cache.py
+++ b/packages/meshbay-node/tests/test_media_cache.py
@@ -1,10 +1,10 @@
-"""Tests for media_cache.py — TMDB/thumbnail cache and its pruning obligation."""
+"""Tests for media_cache.py — TMDB/MusicBrainz/thumbnail cache and its pruning obligation."""
 
 import time
 
 import pytest
 
-from meshbay_node.media_cache import MediaCache, TMDB_META_TTL_SECS
+from meshbay_node.media_cache import MediaCache, TMDB_META_TTL_SECS, MUSICBRAINZ_META_TTL_SECS
 
 
 @pytest.fixture
@@ -69,3 +69,52 @@ async def test_prune_file_removes_thumb_and_mapping_but_not_shared_meta(cache):
     # ep2's own mapping and the shared show metadata both survive
     assert await cache.get_file_tmdb("ep2") == ("555", "tv")
     assert await cache.get_tmdb_meta("555", "tv") == {"name": "A Show"}
+
+
+# ── Music app (docs/musicbay.md §6) — file_mbid/mbid_meta ────────────────────
+
+@pytest.mark.asyncio
+async def test_file_mbid_round_trip(cache):
+    assert await cache.get_file_mbid("file1") is None
+
+    await cache.set_file_mbid("file1", "release-mbid-1")
+
+    assert await cache.get_file_mbid("file1") == "release-mbid-1"
+
+
+@pytest.mark.asyncio
+async def test_mbid_meta_round_trip(cache):
+    assert await cache.get_mbid_meta("release-mbid-1") is None
+
+    await cache.set_mbid_meta("release-mbid-1", {"artist": "Some Artist", "album": "An Album"})
+
+    meta = await cache.get_mbid_meta("release-mbid-1")
+    assert meta == {"artist": "Some Artist", "album": "An Album"}
+
+
+@pytest.mark.asyncio
+async def test_mbid_meta_expires_after_ttl(cache):
+    await cache._db.execute(
+        "INSERT INTO mbid_meta (mbid, json, fetched_at) VALUES (?, ?, ?)",
+        ("old-mbid", '{"album": "Old"}', time.time() - MUSICBRAINZ_META_TTL_SECS - 1),
+    )
+    await cache._db.commit()
+
+    assert await cache.get_mbid_meta("old-mbid") is None
+
+
+@pytest.mark.asyncio
+async def test_prune_file_removes_mbid_mapping_but_not_shared_meta(cache):
+    # Two tracks of the same release share one mbid_meta row.
+    await cache.set_file_mbid("track1", "release-mbid-1")
+    await cache.set_file_mbid("track2", "release-mbid-1")
+    await cache.set_mbid_meta("release-mbid-1", {"album": "An Album"})
+    await cache.put_thumb("cover-hash", "track1", b"cover-bytes")
+
+    await cache.prune_file("track1")
+
+    assert await cache.get_file_mbid("track1") is None
+    assert await cache.get_thumb("cover-hash") is None
+    # track2's own mapping and the shared release metadata both survive
+    assert await cache.get_file_mbid("track2") == "release-mbid-1"
+    assert await cache.get_mbid_meta("release-mbid-1") == {"album": "An Album"}