Downloads with no album (regular YouTube videos, fan edits, etc) left a blank
album, which trips up players like Plexamp. yt_download now appends
--parse-metadata "%(album|Unknown Album)s:%(meta_album)s" so the native/resolved
album is kept when present, else 'Unknown Album' is embedded. Applies to all
download paths (search, playlist, single URL).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>