Serial commands:
- dump: show button and LED state
- ledon/ledoff: toggle all LEDs
- ledtest: sequential LED test
- read: raw button read
- probe: check pin states and test LD toggle
- New PixelStompMux class with shift register read/write
- Read 10 buttons via DI (active LOW)
- Drive 10 LEDs via DAT (shift out + latch)
- LED startup animation uses MUX
- Switch polling reads from MUX shift register
- MUX instance shared between switch and LED drivers
- Remove TinyUSBDevice.begin() conflict with Arduino core
- Switch stub now reads GPIO with debounce (pins 1-10)
- LED stub now drives GPIO pins (pins 11-20) with startup animation
- All pins printed to console on init
- Replace ESP-IDF structure with PlatformIO (platformio.ini)
- Move source files to src/ and include/
- Move libraries to lib/ directory
- Replace FreeRTOS with Arduino task/vTaskDelay
- Use Arduino MIDI library instead of raw TinyUSB
- Dual-core: MIDI on core 0, controller on core 1