triggerButtonlessDfu

Connects to the device running normal firmware and writes to the Buttonless DFU characteristic so the bootloader takes over. The device disconnects and reboots.

Per the Nordic Secure DFU spec, indications must be enabled on the Buttonless DFU characteristic before writing the Enter DFU command. The device validates the CCCD and rejects the write with ATTERR_CPS_CCCD_CONFIG_ERROR if indications are not enabled.

After writing the trigger, the device may disconnect before the indication response arrives — this race condition is expected and handled gracefully.

The caller must have already released the mesh-service BLE connection before calling this.