feat(node): add audio_root, gate Music enrichment on it like video_root

musicbay.md's original call — Music needs no root, tag reads are cheap so
just cover the whole shared tree — didn't hold up against a real messy
library: everything under every shared folder got mixed together with no
way to scope Music down to an actual music collection. This adds an
audio_root setting, symmetric to video_root in every respect: signed
operator op (audio_root/audio_root_ack, MNP bumped to 0.10), validated
against a real directory in the group's own roots before a signature is
even asked for, gates tag/cover enrichment exactly like video_root gates
ffprobe/TMDB (nothing runs until it's set, only files under it once it
is), and a set/change fires a one-off sweep of whatever the folder already
contains.

The old trigger — sweep everything the instant "music" joins enabled_apps
— is gone along with the root-less design it belonged to; setting
audio_root is now the trigger, mirroring set_video_root's
enrich_video_root_fn exactly.

Test coverage mirrors the video_root suite: policy (refuse before a
signature round trip, accept/store correctly) and the enrichment gate
itself (nothing without a root, only files under it, sweep on set).

1 files changed, 137 insertions, 0 deletions

diff --git a/packages/meshbay-node/tests/test_audio_root_policy.py b/packages/meshbay-node/tests/test_audio_root_policy.py
new file mode 100644
index 0000000..73bbe1f
--- /dev/null
+++ b/packages/meshbay-node/tests/test_audio_root_policy.py
@@ -0,0 +1,137 @@
+"""
+Which folder (possibly a subfolder of a shared root) is the Music app's
+entry point for a group. Same shape as test_video_root_policy.py — a
+signed operator instruction, per-group, stored via roster.py's
+group_settings table, added later once a real messy library showed
+musicbay.md's original "no root, whole shared tree" call was wrong.
+"""
+
+from pathlib import Path
+
+import pytest
+
+from meshbay_common.adminop import OP_AUDIO_ROOT
+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)
+    (shared_root / "Music").mkdir()
+    (shared_root / "Podcasts").mkdir()
+    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 = None
+    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_path_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_audio_root({})
+
+    assert not issued
+    assert [m for m in session.sent if m.get("type") == "error"]
+
+
+async def test_a_nonexistent_folder_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_audio_root({"path": "shared/Nonexistent"})
+
+    assert not issued, "a mistyped path must be refused before a signature round trip"
+    assert [m for m in session.sent if m.get("type") == "error"]
+
+
+async def test_path_traversal_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_audio_root({"path": "../../etc"})
+
+    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_audio_root({"path": "shared/Music"})
+
+    assert [m for m in session.sent if m.get("type") == "error"]
+
+
+# ── Accepted cases ───────────────────────────────────────────────────────────
+
+async def test_an_empty_path_is_always_accepted(tmp_path):
+    """Empty means 'unset' — Music shows nothing yet, always valid to clear."""
+    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_audio_root({"path": ""})
+
+    assert issued == [(OP_AUDIO_ROOT, "")]
+
+
+async def test_a_real_subfolder_is_accepted_and_signed(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_audio_root({"path": "shared/Music"})
+
+    assert issued == [(OP_AUDIO_ROOT, "shared/Music")]
+
+
+# ── 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.audio_root("g1") == "", "absent must mean unset"
+        await roster.set_audio_root("g1", "shared/Music", set_by="op")
+        assert await roster.audio_root("g1") == "shared/Music"
+    finally:
+        await roster.close()
+
+    reopened = Roster(db_path=tmp_path / "roster.db")
+    await reopened.open()
+    try:
+        assert await reopened.audio_root("g1") == "shared/Music"
+        assert await reopened.audio_root("g2") == "", "one group's setting must not answer for another"
+    finally:
+        await reopened.close()