Fix MusicBrainz artist detail showing MBID as name

URL-driven routing (PR #644) no longer passes the display name as a query
param to the artist-detail endpoint. The source-only detail builder fell back
to artist_id when artist_name was empty, surfacing the raw MBID as the page
title for MusicBrainz artists.

Two fixes in build_source_only_artist_detail:
- Drop the artist_id fallback in resolved_name so an MBID can never become
  the display name
- Add a musicbrainz elif branch (matching the Spotify/Deezer/iTunes pattern)
  that calls MusicBrainzSearchClient.get_artist() to resolve the real name
  and genres from the MBID when no name is provided

core/artist_source_detail.py

@@ -52,7 +52,7 @@ def build_source_only_artist_detail(
     ``jsonify`` or equivalent. Status is 200 on success, 404 when the
     source's discography lookup returned no releases.
     """
-    resolved_name = (artist_name or artist_id or "").strip()
+    resolved_name = (artist_name or "").strip()
 
     # 1. Image URL via the same helper /api/artist/<id>/image uses.
     image_url: Optional[str] = None
@@ -101,6 +101,17 @@ def build_source_only_artist_detail(
                 source_genres = az_artist.get("genres") or []
                 if not image_url and az_artist.get("images"):
                     image_url = az_artist["images"][0].get("url")
+        elif source == "musicbrainz":
+            try:
+                from core.musicbrainz_search import MusicBrainzSearchClient
+                mb = MusicBrainzSearchClient()
+                mb_artist = mb.get_artist(artist_id)
+                if mb_artist:
+                    if not artist_name and mb_artist.get("name"):
+                        resolved_name = mb_artist["name"]
+                    source_genres = mb_artist.get("genres") or []
+            except Exception as e:
+                logger.debug(f"MusicBrainz artist info lookup failed for {artist_id}: {e}")
     except Exception as e:
         logger.debug(f"Source-side artist info lookup failed for {source}:{artist_id}: {e}")
 

webui/static/helper.js

@@ -3416,6 +3416,7 @@ const WHATS_NEW = {
     '2.5.6': [
         { date: 'May 18, 2026 — 2.5.6 release' },
         { title: 'MusicBrainz as Primary Metadata Source', desc: 'MusicBrainz is now a full primary metadata source on equal footing with Deezer, iTunes, Spotify, and Discogs. switch to it in Settings → Metadata Source — always available, no account or API key needed, rate-limited to 1 req/sec. covers all primary source flows: search, album/track/artist lookup, watchlist scans, discover hero, similar artist backfill, artist map.', page: 'settings' },
+        { title: 'Fix: MusicBrainz artist detail showing MBID as name', desc: 'clicking a MusicBrainz artist from search results was showing the raw MBID as the artist name on the detail page. URL-driven routing (PR #644) no longer passes the display name to the backend, so the source detail endpoint now looks it up directly from MusicBrainz by MBID.' },
     ],
     '2.5.5': [
         { date: 'May 17, 2026 — 2.5.5 release' },