OtaControl

Firmware-update control opcodes for GattUuids.FIRMWARE_UPDATE_SERVICE (vendor OTA contract, ported from the C SDK's ota_update.hpp).

The host writes REQUEST / DONE to the control characteristic; the device answers with the corresponding ACK/NAK code as a notification on the status characteristic. Firmware bytes travel as plain (MTU - 3)-byte writes to the packet characteristic between the two control writes. There is no CRC or resume: integrity rests on the ATT write-with-response acks, and an interrupted transfer leaves the previous firmware in place.