fix(track-picker): allow inserting link-only tracks (Spotify/YouTube, no hosted file)
The "Insert track" picker disabled any track without a hosted media file (playable = !!filename), so
a link-only track (external Spotify/YouTube, 0:00) couldn't be inserted — even though [[track:]]
renders its link card fine on the post. Now a track is insertable if it has a file OR a link.
Co-Authored-By: Claude <noreply@…>