fix(node): say so when MusicBrainz lookups are inert

Staying inert without a contact is the documented policy (module docstring,
musicbay.md §3.1): the usage policy wants a contact in the User-Agent, so an
unidentified client is never sent. Staying *silent* about it was not a
decision — the operator sees Music tiles with no metadata or cover art and
has nothing to search the logs for.

Warns once per client rather than once per lookup, since the condition is
constant for the client's lifetime.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DtfG7z6wHWj8RKHCvxQtY1

1 files changed, 13 insertions, 1 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/musicbrainz.py b/packages/meshbay-node/src/meshbay_node/musicbrainz.py
index 59f3778..d5ca1e9 100644
--- a/packages/meshbay-node/src/meshbay_node/musicbrainz.py
+++ b/packages/meshbay-node/src/meshbay_node/musicbrainz.py
@@ -105,12 +105,24 @@ class MusicBrainzClient:
         self._client = httpx.AsyncClient(timeout=_TIMEOUT, transport=transport)
         self._rate_lock = asyncio.Lock()
         self._last_request_monotonic: float | None = None
+        self._warned_no_contact = False
 
     async def close(self) -> None:
         await self._client.aclose()
 
     async def _resolve_contact(self) -> str | None:
-        return self._owner_email or None
+        if self._owner_email:
+            return self._owner_email
+        # Staying inert is deliberate (see the module docstring), but doing it
+        # silently is not: the operator sees Music tiles with no metadata and
+        # nothing anywhere says why. Once per client, not per lookup.
+        if not self._warned_no_contact:
+            self._warned_no_contact = True
+            log.warning(
+                "MusicBrainz lookups are inert: the node owner's hub account has "
+                "no email on file, and the usage policy requires a contact in the "
+                "User-Agent. Music tiles will show no metadata or cover art.")
+        return None
 
     async def _pace(self) -> None:
         """Serializes every call through this client to >= _MIN_INTERVAL_SECS apart."""