fix(node,hub): key music/media metadata lookups by file_id, not path

IndexEntry.path is the *folder* a file is in (indexer.py's
_virtual_dir docstring: "the directory a file appears in"), not the
file itself. GroupIndex.get_entry_by_path() treated it as if it named
one file, and every one of its four callers did too:
_do_music_meta_request, _do_media_meta_request, _do_tmdb_override, and
_admin_exec_tmdb_override. Any two files sharing a folder — an album is
one folder with many tracks, a season is one folder with many episodes
— collided: a lookup by path silently returned whichever entry the
index happened to iterate to first, regardless of which file the
client actually asked about.

Found live (2026-08-25): three unrelated albums ("High Tone - Various",
two "Le Peuple de l'Herbe" albums) all showed the same MusicBrainz
cover, because all their representative tracks happened to sit in one
"high_tone" folder alongside a track that legitimately matched that
cover. A force-reload didn't help — the bug is server-side, not a
stale client state.

Fixed by keying these four request/response pairs by `file_id` (the
entry's own content hash — already unique, already how every other
lookup in the system identifies a file) instead of `path`, both in the
wire messages (music_meta_req/resp, media_meta_req/resp, tmdb_override)
and in music-app.js/video-app.js's own hooks. GroupIndex.get_entry_by_path
is now unused and removed — GroupIndex.get_entry(file_id) already did
the right thing.

No test previously exercised either handler with two entries sharing a
folder — the only existing coverage (test_tmdb_override_policy.py) gave
each entry its own folder, so the bug never had a chance to show up.
Added that scenario there and in two new test files, all confirmed
failing against the pre-fix code before being confirmed green against
the fix.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013XSohfUQQiaE77qyFLgSv3

1 files changed, 0 insertions, 13 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/indexer/group_index.py b/packages/meshbay-node/src/meshbay_node/indexer/group_index.py
index 1ce4e0a..25081ef 100644
--- a/packages/meshbay-node/src/meshbay_node/indexer/group_index.py
+++ b/packages/meshbay-node/src/meshbay_node/indexer/group_index.py
@@ -78,19 +78,6 @@ class GroupIndex:
     def get_entry(self, file_id: str) -> IndexEntry | None:
         return self._entries.get(file_id)
 
-    def get_entry_by_path(self, path: str) -> IndexEntry | None:
-        """
-        Linear scan — entries are keyed by content id, not path, and nothing
-        before the Videos app needed to go the other way (a client always
-        already has the id from index_sync/index_delta). Fine for an
-        on-demand, per-tile lookup against a few thousand entries; revisit
-        if a future caller makes this hot.
-        """
-        for entry in self._entries.values():
-            if entry.path == path:
-                return entry
-        return None
-
     @property
     def entries(self) -> list[IndexEntry]:
         return list(self._entries.values())