Architecture changes:
- config/: Centralized pin definitions and settings
- hal/: Hardware abstraction layer (servo PWM control)
- drivers/: Device drivers (hand, emg_sensor)
- core/: Business logic (gestures)
- app/: Application entry point
New features:
- Fake EMG data streaming over USB serial at ~100 Hz
- FEATURE_FAKE_EMG flag to switch between fake/real sensors
- Python RealSerialStream class for receiving serial data
Data format: timestamp_ms,ch0,ch1,ch2,ch3
