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, 126 insertions, 0 deletions

diff --git a/packages/meshbay-node/tests/test_musicbrainz_enabled_policy.py b/packages/meshbay-node/tests/test_musicbrainz_enabled_policy.py
new file mode 100644
index 0000000..e86a3f3
--- /dev/null
+++ b/packages/meshbay-node/tests/test_musicbrainz_enabled_policy.py
@@ -0,0 +1,126 @@
+"""
+Whether MusicBrainz lookups run *at all* for a group — docs/musicbay.md
+§3.2/§6. Per-group from the start (unlike tmdb_enabled, which started
+node-wide and moved per-group later once the lesson was already learned).
+Same shape as test_tmdb_enabled_policy.py: a signed operator instruction,
+scoped to self._group_id (not passed explicitly on the wire), stored via
+roster.py's group_settings table under the real group_id.
+
+The contact string stays node-wide — see test_musicbrainz_config_policy.py.
+"""
+
+from pathlib import Path
+
+import pytest
+
+from meshbay_common.adminop import OP_MUSICBRAINZ_ENABLED
+from meshbay_node.indexer.group_index import GroupIndex
+from meshbay_node.roster import Roster
+from meshbay_node.transport.webrtc_server import WebRTCPeerSession
+from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
+
+from conftest import one_root
+
+pytestmark = pytest.mark.asyncio
+
+
+def _session(tmp_path: Path, user_id: str, *, operator: str | None = None) -> WebRTCPeerSession:
+    shared_root = tmp_path / "shared"
+    shared_root.mkdir(exist_ok=True)
+    index = GroupIndex(group_id="g" * 32, sk_node=Ed25519PrivateKey.generate())
+    ctx = {
+        "roots": one_root(shared_root),
+        "index": index,
+        "sk_node": index.sk_node,
+        "node_user_id": operator,
+    }
+    session = WebRTCPeerSession.__new__(WebRTCPeerSession)
+    session._ctx = ctx
+    session._group_id = "g" * 32
+    session._user_id = user_id
+    session._pk_user = ""
+    session.sent = []
+    session._send = session.sent.append
+    session._audit = lambda *a, **k: None
+    return session
+
+
+# ── Refused before a challenge is even issued ───────────────────────────────
+
+async def test_missing_enabled_is_refused(tmp_path):
+    session = _session(tmp_path, "op", operator="op")
+    session._has_admin_authority = lambda: True
+    issued = []
+    session._issue_admin_challenge = lambda op, subject: issued.append((op, subject))
+
+    session._do_musicbrainz_enabled({})
+
+    assert not issued
+    assert [m for m in session.sent if m.get("type") == "error"]
+
+
+async def test_non_bool_enabled_is_refused(tmp_path):
+    session = _session(tmp_path, "op", operator="op")
+    session._has_admin_authority = lambda: True
+    issued = []
+    session._issue_admin_challenge = lambda op, subject: issued.append((op, subject))
+
+    session._do_musicbrainz_enabled({"enabled": "yes"})
+
+    assert not issued
+    assert [m for m in session.sent if m.get("type") == "error"]
+
+
+async def test_a_request_with_nobody_to_authorize_it_is_refused(tmp_path):
+    session = _session(tmp_path, "member-1", operator="the-operator")
+    session._has_admin_authority = lambda: False
+
+    session._do_musicbrainz_enabled({"enabled": False})
+
+    assert [m for m in session.sent if m.get("type") == "error"]
+
+
+# ── Accepted cases ───────────────────────────────────────────────────────────
+
+async def test_a_valid_request_is_signed_against_this_groups_id(tmp_path):
+    session = _session(tmp_path, "op", operator="op")
+    session._has_admin_authority = lambda: True
+    issued = []
+    session._issue_admin_challenge = lambda op, subject: issued.append((op, subject))
+
+    session._do_musicbrainz_enabled({"enabled": True})
+
+    assert issued == [(OP_MUSICBRAINZ_ENABLED, "True")]
+
+
+async def test_disabling_is_signed_too(tmp_path):
+    session = _session(tmp_path, "op", operator="op")
+    session._has_admin_authority = lambda: True
+    issued = []
+    session._issue_admin_challenge = lambda op, subject: issued.append((op, subject))
+
+    session._do_musicbrainz_enabled({"enabled": False})
+
+    assert issued == [(OP_MUSICBRAINZ_ENABLED, "False")]
+
+
+# ── Where it is stored ──────────────────────────────────────────────────────
+
+async def test_the_setting_lives_on_the_node_and_survives_a_restart(tmp_path):
+    roster = Roster(db_path=tmp_path / "roster.db")
+    await roster.open()
+    try:
+        assert await roster.musicbrainz_enabled("g1") is True, "absent must mean on"
+        await roster.set_musicbrainz_enabled("g1", False, set_by="op")
+        assert await roster.musicbrainz_enabled("g1") is False
+    finally:
+        await roster.close()
+
+    reopened = Roster(db_path=tmp_path / "roster.db")
+    await reopened.open()
+    try:
+        assert await reopened.musicbrainz_enabled("g1") is False
+        assert await reopened.musicbrainz_enabled("g2") is True, \
+            "one group's setting must not answer for another"
+    finally:
+        await reopened.close()