As per my understanding, 19 stands for HCI WICED Packet. 0A is the operating code for Unbond command as you are using code HCI_CONTROL_COMMAND_UNBOND. 00 is the group code suggesting group HCI_CONTROL_GROUP_DEVICE. Next bytes are the packet length.
Please check WICED HCI UART Control Protocol document Page 16 for more details (/20719-B1_Bluetooth/doc/WICED-HCI-Control-Protocol.pdf).
What it is and how it is formed I understand.
The question is, how do I disable sending the header when sending data to UART?
What if I just want to send my bytes buffer without any additional automatically generated bytes?
The question is still relevant. Can you please help me sort it out?