fix: populate albumArtist in metadata editor via getAlbum fallback

getSong often omits albumArtist; getAlbum always returns album.artist.
Enrich the song object before showing the edit form.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui.js

@@ -281,6 +281,13 @@ export async function showSongInfo(s) {
     const r = await api('getSong', `&id=${s.id}`);
     const full = r.song;
     if (full) {
+      // getSong often omits albumArtist — fill it from getAlbum which always has album.artist
+      if (!full.albumArtist && full.albumId) {
+        try {
+          const ar = await api('getAlbum', `&id=${full.albumId}`);
+          if (ar.album?.artist) full.albumArtist = ar.album.artist;
+        } catch {}
+      }
       S.infoSong = full;
       _renderInfoModal(full);
       // If edit mode was already opened before getSong returned, refresh the fields