fix: radio mode uses getSimilarSongs2 for artist/genre-aware playback

- Dedup now checks only the last 50 queued songs instead of the entire
  queue, so the radio doesn't stall on small libraries once every similar
  song has been seen
- If every candidate is a recent duplicate (tiny library), allow up to 5
  repeats rather than returning empty and letting the queue run dry
- Add second _queueGen guard after the getRandomSongs fallback await

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

src/player.js

@@ -641,22 +641,31 @@ export async function fillRadioQueue() {
   try {
     const seed = S.queue[S.qIdx];
     let newSongs = [];
+
+    // 1. Try similar songs seeded from the current track
     if (seed?.id) {
       const r = await api('getSimilarSongs2', `&id=${seed.id}&count=20`);
       newSongs = r.similarSongs2?.song || [];
     }
-    // Fall back to random if similar songs unavailable (no Last.fm config, unknown track, etc.)
+    if (gen !== _queueGen) return;
+
+    // 2. Fall back to random if similar songs unavailable or empty
     if (!newSongs.length) {
       const r = await api('getRandomSongs', '&size=20');
       newSongs = r.randomSongs?.song || [];
     }
-    // Bail if playQueue() was called while we were awaiting — appending to a
-    // replaced queue would desync native (setQueue already wiped the old one).
     if (gen !== _queueGen) return;
-    // Deduplicate against songs already queued
-    const existingIds = new Set(S.queue.map(s => s.id));
-    newSongs = newSongs.filter(s => !existingIds.has(s.id));
     if (!newSongs.length) return;
+
+    // Deduplicate only against the last 50 queued songs so the radio never
+    // stalls on a small library. Songs cycle back after ~50 tracks rather than
+    // blocking forever once they've been seen once.
+    const recentIds = new Set(S.queue.slice(-50).map(s => s.id));
+    const deduped = newSongs.filter(s => !recentIds.has(s.id));
+    // If every candidate was a recent duplicate (very small library), allow
+    // repeats rather than letting the queue run dry and music stop.
+    newSongs = deduped.length > 0 ? deduped : newSongs.slice(0, 5);
+
     const prevLen = S.queue.length;
     S.queue.push(...newSongs);
     renderQueue();