Hide YouTube player for custom songs

Skip YouTube attribution and player in both the song selector preview
and the game page when playing a custom (non-YouTube) track.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/features/song-select/SongSelectScreen.tsx

@@ -88,9 +88,11 @@ export function SongSelectScreen() {
         difficulty={activeSong.difficulty}
       />
 
-      <YouTubeAttribution>
-        <div ref={ytPreviewRef} className="song-select-screen__yt-preview" />
-      </YouTubeAttribution>
+      {!activeSong.isCustom && (
+        <YouTubeAttribution>
+          <div ref={ytPreviewRef} className="song-select-screen__yt-preview" />
+        </YouTubeAttribution>
+      )}
 
       <div className="song-select-screen__content">
         <header className="song-select-screen__header">

src/pages/GamePage.tsx

@@ -256,9 +256,11 @@ export function GamePage() {
       <canvas ref={arCanvasRef} className="ar-overlay" />
 
       {/* YouTube video player (visible to comply with YT ToS) */}
-      <YouTubeAttribution>
-        <div ref={ytHostRef} className={styles.ytPlayer} />
-      </YouTubeAttribution>
+      {!resolvedSong.isCustom && (
+        <YouTubeAttribution>
+          <div ref={ytHostRef} className={styles.ytPlayer} />
+        </YouTubeAttribution>
+      )}
 
       {(calibrationStatus === 'framing') && (
         <div className="framing-line" />