Ambient soundtrack for DeepSeek Harness

Key features

• A track is never interrupted by a state change.
• music_play(library) — the model scores its own work.
• Turns open and close far faster than a song lasts, so cutting mid-track reads as noise instead of feedback.
• The state you are in when a track ends decides what plays next.
• Only an explicit music_stop cuts playback, because silence requested is silence owed.