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