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, 15 insertions, 0 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/roster.py b/packages/meshbay-node/src/meshbay_node/roster.py
index 24424ab..91e18cd 100644
--- a/packages/meshbay-node/src/meshbay_node/roster.py
+++ b/packages/meshbay-node/src/meshbay_node/roster.py
@@ -649,6 +649,21 @@ class Roster:
         await self.set_setting(group_id, self.SETTING_VIDEO_ROOT, path or "", set_by)
         return path or ""
 
+    # Same shape as SETTING_VIDEO_ROOT — the Music app's own entry point,
+    # added later (docs/musicbay.md's original "no root, works over the
+    # whole shared tree" simplification turned out not to hold up against a
+    # real messy library: the operator asked for the same scoping Videos
+    # already had). Empty/unset means Music shows nothing yet, exactly like
+    # an unset video_root — see daemon.py's enrichment gate.
+    SETTING_AUDIO_ROOT = "audio_root"
+
+    async def audio_root(self, group_id: str) -> str:
+        return await self.get_setting(group_id, self.SETTING_AUDIO_ROOT, "") or ""
+
+    async def set_audio_root(self, group_id: str, path: str, set_by: str = "") -> str:
+        await self.set_setting(group_id, self.SETTING_AUDIO_ROOT, path or "", set_by)
+        return path or ""
+
     # Whether TMDB lookups run for this group at all — per-group, unlike the
     # token/language above: one node process can share a real media library
     # group and several test/demo groups, and outbound TMDB traffic (and API