sendToRadio
Sends a command/packet directly to the radio.
Adds a mesh packet to the queue for sending.
A completed packet ID may be reused by a later retry. A duplicate is rejected only while that ID is still queued or in flight, preserving single ownership of its response.
Return
true when the packet's non-zero ID was reserved and queued, or false when the packet was invalid, its ID was already reserved, the radio is not connected, or the owning service scope has shut down.