fix(stream): enable captions only for real Korean tracks, skip auto-generated

The broadcast subtitle rule treated any ko* track as Korean, so YouTube's
auto-generated (자동 생성) Korean track would switch captions on. Match only
human-authored tracks (kind !== 'asr', vss_id not 'a.*') and pass the full
track object to setOption so YouTube selects the manual track rather than the
same-languageCode ASR one. Captions stay off when only an auto track exists.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

bot/scripts/stream-test/README.md

@@ -29,7 +29,8 @@ real browsing session captured from the X display.
   ad" instantly, closes overlay ads, fast-forwards unskippable ads (seek-to-end
   + 16x + mute) and RESTORES the pre-ad muted/playbackRate when the ad ends; and
   (2) applies the subtitle rule per video: captions OFF by default, Korean ON
-  when the video offers a Korean track. Run it alongside the broadcast; it
+  only when the video offers a real (human-authored) Korean track; YouTube's
+  auto-generated Korean track is ignored. Run it alongside the broadcast; it
   reconnects across Chrome restarts.
 
 ## Run

bot/scripts/stream-test/broadcast-helper.mjs

@@ -5,7 +5,9 @@
 //      so they clear in ~1s. The pre-ad muted/playbackRate are SAVED and
 //      RESTORED when the ad ends, so the main video is never left muted/fast.
 //   2. Applies the subtitle rule per video: captions OFF by default, but a
-//      Korean track is turned ON when the video offers one. Runs once per video.
+//      real (human-authored) Korean track is turned ON when the video offers
+//      one. YouTube's auto-generated (자동 생성) Korean track does NOT count and
+//      is left off. Runs once per video.
 // Self-contained: no extension, no network/hosts changes. Reconnects across
 // Chrome restarts.
 //
@@ -44,29 +46,41 @@ const WATCH = `(() => {
     return adShowing;
   };
 
+  // A "real" Korean caption track is a human-authored/uploaded Korean track,
+  // NOT YouTube's auto-speech-recognition (자동 생성) track. ASR tracks report
+  // kind === 'asr' and a vss_id like 'a.ko'; manual tracks have an empty kind
+  // and a vss_id like '.ko'. We only ever turn captions on for a real track.
+  const isRealKo = (t) => !!t && /^ko/i.test(t.languageCode || '')
+    && t.kind !== 'asr' && !/^a\./.test(t.vss_id || '');
+
   const capTick = (adShowing) => {
     if (adShowing) return;       // don't touch captions while an ad plays
     const p = document.getElementById('movie_player');
     if (!p || !p.getOption || !p.getVideoData) return;
     const vid = p.getVideoData().video_id;
     if (!vid) return;
-    // Decide the desired state once per video (off, or Korean if offered).
+    // Decide the desired state once per video: ON only if a real (non-ASR)
+    // Korean track is offered, otherwise OFF.
     if (capWant[vid] === undefined) {
       capTries[vid] = (capTries[vid] || 0) + 1;
       let tracks = [];
       try { p.loadModule('captions'); tracks = p.getOption('captions', 'tracklist') || []; } catch {}
-      if (tracks.length) capWant[vid] = tracks.find((t) => /^ko/i.test(t.languageCode || '')) ? 'ko' : 'off';
+      if (tracks.length) capWant[vid] = tracks.some(isRealKo) ? 'ko' : 'off';
       else if (capTries[vid] > 16) capWant[vid] = 'off'; // no tracks: keep it off
       else return;               // tracklist not ready yet
     }
-    // Enforce it every tick so YouTube cannot silently re-enable captions.
+    // Enforce it every tick so YouTube cannot silently re-enable captions or
-    let curLc = '';
+    // swap our manual Korean track for the auto-generated one.
-    try { const c = p.getOption('captions', 'track'); curLc = (c && c.languageCode) || ''; } catch {}
+    let curTrack = null;
+    try { curTrack = p.getOption('captions', 'track'); } catch {}
+    const curLc = (curTrack && curTrack.languageCode) || '';
     if (capWant[vid] === 'ko') {
-      if (!/^ko/i.test(curLc)) {
+      if (!isRealKo(curTrack)) {  // not on the real Korean track (off, or ASR) -> set it
         let tracks = []; try { tracks = p.getOption('captions', 'tracklist') || []; } catch {}
-        const ko = tracks.find((t) => /^ko/i.test(t.languageCode || ''));
+        const ko = tracks.find(isRealKo);
-        if (ko) { try { p.setOption('captions', 'track', { languageCode: ko.languageCode }); } catch {} }
+        // Pass the full track object so YouTube selects this exact manual track
+        // and not the same-languageCode auto-generated one.
+        if (ko) { try { p.setOption('captions', 'track', ko); } catch {} }
       }
     } else if (curLc) {          // want off but a track is on -> turn it off
       try { p.setOption('captions', 'track', {}); } catch {}