Protocol update adds FFE4 Status format: 7×PD sensors (little-endian)
+ VBAT battery voltage (mV) + XOR checksum = 17 bytes.
- parseVendorStatus: handles 1-byte heartbeat, 17-byte ADC, 33-byte params
- handleValueChange: ADC type extracts PD array + battery % from VBAT
- Battery calculated as linear 3000mV(0%) to 4200mV(100%)
- PD data passed through status event for treatment pages
- Updated protocol doc with full byte table and old/new comparison
- discoverChars uses properties (write/notify) to distinguish FFE1
command characteristic from FFE1 service UUID
- handleValueChange: vendor_33 mode emits vendor_status (FFE4 heartbeat)
and vendor_data separately, no longer tries parseFrame on raw bytes
- parseVendorStatus handles 1-byte heartbeat and 33-byte state readback
with proper IO1-IO5 field parsing