fix(now-playing): split artist links and About the Artist tabs (#960)

* fix(now-playing): split artist links and About the Artist tabs

OpenSubsonic artists[] now drives per-artist navigation on Now Playing
hero and the queue current-track row (matching player bar). About the
Artist loads bio for each performer via tabs when a track has multiple
artist ids; queue Info uses the primary ref for bio/tour fetch.

Reported by zunoz on the Psysonic Discord (v1.47.0-rc.3).

* docs: note Now Playing multi-artist fix in CHANGELOG (PR #960)

src/hooks/useArtistInfoBatch.ts

@@ -0,0 +1,85 @@
+import { useEffect, useMemo, useState } from 'react';
+import { getArtistInfoForServer } from '../api/subsonicArtists';
+import type { SubsonicArtistInfo, SubsonicOpenArtistRef } from '../api/subsonicTypes';
+import { makeCache } from '../utils/cache/nowPlayingCache';
+
+const artistInfoCache = makeCache<SubsonicArtistInfo | null>();
+
+function cacheKey(serverId: string, artistId: string): string {
+  return `${serverId}:${artistId}`;
+}
+
+/**
+ * Fetches `getArtistInfo` for each ref with an id. Returns `undefined` for ids
+ * still loading, `null` when fetch finished with no info.
+ */
+export function useArtistInfoBatch(
+  serverId: string | undefined,
+  refs: SubsonicOpenArtistRef[],
+  similarArtistCount?: number,
+): Record<string, SubsonicArtistInfo | null | undefined> {
+  const ids = useMemo(
+    () => [...new Set(refs.map(r => r.id?.trim()).filter((id): id is string => Boolean(id)))],
+    [refs],
+  );
+  const idsKey = ids.join('\x1e');
+
+  const [byId, setById] = useState<Record<string, SubsonicArtistInfo | null | undefined>>(() => {
+    if (!serverId || ids.length === 0) return {};
+    const seed: Record<string, SubsonicArtistInfo | null | undefined> = {};
+    for (const id of ids) {
+      const cached = artistInfoCache.get(cacheKey(serverId, id));
+      if (cached !== undefined) seed[id] = cached;
+    }
+    return seed;
+  });
+
+  useEffect(() => {
+    if (!serverId || ids.length === 0) {
+      setById({});
+      return;
+    }
+
+    const next: Record<string, SubsonicArtistInfo | null | undefined> = {};
+    const pending: string[] = [];
+    for (const id of ids) {
+      const cached = artistInfoCache.get(cacheKey(serverId, id));
+      if (cached !== undefined) {
+        next[id] = cached;
+      } else {
+        next[id] = undefined;
+        pending.push(id);
+      }
+    }
+    setById(next);
+
+    if (pending.length === 0) return;
+
+    let cancelled = false;
+    void Promise.all(
+      pending.map(async id => {
+        try {
+          const info = await getArtistInfoForServer(serverId, id, {
+            similarArtistCount: similarArtistCount,
+          });
+          artistInfoCache.set(cacheKey(serverId, id), info ?? null);
+          return [id, info ?? null] as const;
+        } catch {
+          artistInfoCache.set(cacheKey(serverId, id), null);
+          return [id, null] as const;
+        }
+      }),
+    ).then(results => {
+      if (cancelled) return;
+      setById(prev => {
+        const merged = { ...prev };
+        for (const [id, info] of results) merged[id] = info;
+        return merged;
+      });
+    });
+
+    return () => { cancelled = true; };
+  }, [serverId, idsKey, similarArtistCount]);
+
+  return byId;
+}

src/hooks/useNowPlayingPrewarm.ts

@@ -12,6 +12,7 @@ import { prewarmNowPlayingFetchers } from './useNowPlayingFetchers';
 import { useAuthStore } from '../store/authStore';
 import { usePlayerStore } from '../store/playerStore';
 import { usePlaybackServerId } from './usePlaybackServerId';
+import { primaryTrackArtistRef } from '../utils/playback/trackArtistRefs';
 
 const NOW_PLAYING_COVER_CSS_PX = 800;
 
@@ -52,11 +53,12 @@ export function useNowPlayingPrewarm(): void {
   useEffect(() => {
     if (!currentTrack || !playbackServerId) return;
 
+    const primary = primaryTrackArtistRef(currentTrack);
     void prewarmNowPlayingFetchers({
       songId: currentTrack.id,
-      artistId: currentTrack.artistId,
+      artistId: primary.id,
       albumId: currentTrack.albumId,
-      artistName: currentTrack.artist,
+      artistName: primary.name ?? currentTrack.artist,
       enableBandsintown,
       audiomuseNavidromeEnabled,
       lastfmUsername,
@@ -81,6 +83,7 @@ export function useNowPlayingPrewarm(): void {
   }, [
     currentTrack?.id,
     currentTrack?.artistId,
+    currentTrack?.artists,
     currentTrack?.albumId,
     currentTrack?.coverArt,
     currentTrack?.artist,