PlatformIO's built-in upload breaks on the S2 Mini (1200bps USB
touch reset disconnects the native USB port). All flash targets
now call esptool directly with the correct S2 partition offsets:
bootloader at 0x1000, firmware at 0x10000, LittleFS at 0x290000.
Also adds USB.begin() before Serial.begin() in main.cpp — required
for ESP32-S2 native USB-CDC to initialize properly.
- Add #include <USB.h> to all .cpp files (required for HWCDCSerial)
- Use ESP-IDF v5.x esp_task_wdt_config_t struct instead of removed API
- Remove duplicate ARDUINO_USB_MODE/CDC flags from platformio.ini
(board definition already provides these)
