TLS connection + 8-byte native-order length-prefixed framing to the
controller, verified byte-for-byte against request.c's own framing
and myapp.c's client TLS posture (SSL_VERIFY_NONE, no CN check).
Opcode-agnostic: moves raw bytes only, so the same send_request()
serves both OP_upgradeConfig and ProbeConfigTag's direct-struct
variant. Connection always closes on error, including handshake
timeout.
