- DrumDetector.cs: 3-band onset detection (kick/snare/brass) with adaptive
thresholds, per-sub-tick timing within 100ms frames
- Kick: low-band onset, 150ms deep thump
- Snare: broadband (mid+high) onset, 50ms mid punch
- Brass: high-only onset, 10ms buzzy
- Priority: kick > snare > brass when multiple hit same sub-tick
- Intensity = max (100) on hit, 0 on silence — user limiter scales down
- MusicAnalyzer: add BuildMelodyFrame for chB only (pitch+energy)
- LiveCapture: chA now from DrumDetector, chB unchanged (melody)
- Sub-tick mapping: FFT window position → 0-3 within each 100ms tick
