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).

3 files changed, 15 insertions, 1 deletions

diff --git a/packages/meshbay-common/src/meshbay_common/__init__.py b/packages/meshbay-common/src/meshbay_common/__init__.py
index ecf51fd..b37de8e 100644
--- a/packages/meshbay-common/src/meshbay_common/__init__.py
+++ b/packages/meshbay-common/src/meshbay_common/__init__.py
@@ -37,5 +37,11 @@ __version__ = "0.7.0"
 # way a TMDB poster or MusicBrainz cover is cached. Additive: an older
 # client never sends the request, and simply can't play those two formats,
 # same as before this existed.
-MNP_VERSION = "0.9"
+# 0.10: added `audio_root`/`_ack` — the Music app's own entry point, same
+# shape as `video_root`/`_ack`. Reverses musicbay.md's original "no root,
+# whole shared tree" call: a real messy library showed that call was
+# wrong, and Music now requires one before showing/enriching anything,
+# exactly like Videos. Additive at the protocol level: an older client
+# never sends the op and never expects the field.
+MNP_VERSION = "0.10"
 MHP_VERSION = "0.1"
diff --git a/packages/meshbay-common/src/meshbay_common/adminop.py b/packages/meshbay-common/src/meshbay_common/adminop.py
index f0a79fe..d09b95e 100644
--- a/packages/meshbay-common/src/meshbay_common/adminop.py
+++ b/packages/meshbay-common/src/meshbay_common/adminop.py
@@ -92,6 +92,10 @@ OP_MUSICBRAINZ_CONFIG = "musicbrainz_config"
 # the lesson was already learned once). Signed for the same reason as
 # tmdb_enabled.
 OP_MUSICBRAINZ_ENABLED = "musicbrainz_enabled"
+# Which folder is the Music app's entry point for this group — same shape as
+# OP_VIDEO_ROOT above, added later once a real messy library showed the
+# "no root, whole shared tree" simplification didn't hold up.
+OP_AUDIO_ROOT = "audio_root"
 OP_ROOT_ADD = "root_add"
 OP_ROOT_REMOVE = "root_remove"
 OP_GROUP_ATTACH = "group_attach"
diff --git a/packages/meshbay-common/src/meshbay_common/protocol.py b/packages/meshbay-common/src/meshbay_common/protocol.py
index 8f29c38..24fea8f 100644
--- a/packages/meshbay-common/src/meshbay_common/protocol.py
+++ b/packages/meshbay-common/src/meshbay_common/protocol.py
@@ -119,6 +119,10 @@ class MNP:
     # TMDB poster or a MusicBrainz cover.
     AUDIO_TRANSCODE_REQ = "audio_transcode_req"          # client → node: transcode this file id
     AUDIO_TRANSCODE_RESP = "audio_transcode_resp"        # node → client: cache hash/size/mime
+    # Which folder is the Music app's entry point for this group — same
+    # shape as VIDEO_ROOT above.
+    AUDIO_ROOT            = "audio_root"                  # operator → node: which folder is the Music entry point
+    AUDIO_ROOT_ACK        = "audio_root_ack"
     # Device linking. A new device files a request bound to a code it displays;
     # an already-pinned device of the same account approves it. Neither the hub
     # nor the node can produce the countersignature.