feat: track column buttons, ghost playback, per-track channels

- Track column: centered 12px buttons, purple active / yellow highlight
- Ghost playback: ghostLayers synced to st.ghostPlayLayers via useEffect;
  schedulePianoRollMidi plays ghost notes from active tracks
- Per-track MIDI channels: each track gets a unique channel based on
  its index, enabling separate instruments per track
This commit is contained in:
2026-07-27 18:21:46 +07:00
parent a98dd58744
commit 0500d16bc7
2 changed files with 64 additions and 9 deletions
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