connect_op.hpp is missing the start_clean configuration feature.

void send_connect() {
auto packet = control_packet::of(
no_pid, get_allocator(),
encoders::encode_connect,
_ctx.creds.client_id,
_ctx.creds.username, _ctx.creds.password,
_ctx.keep_alive, false, _ctx.co_props, _ctx.will_msg
);
the "false" is const, should be modified:
void send_connect() {
auto packet = control_packet::of(
no_pid, get_allocator(),
encoders::encode_connect,
_ctx.creds.client_id,
_ctx.creds.username, _ctx.creds.password,
_ctx.keep_alive, _ctx.start_clean, _ctx.co_props, _ctx.will_msg
);

Start in connect_op.hpp at send_connect(), where the CONNECT packet is assembled and the hard-coded false value is passed to encoders::encode_connect. Trace the existing start_clean configuration in the connection context, then verify that the packet uses it and run the repository's relevant MQTT connection tests. Done means start_clean controls the generated CONNECT packet instead of a constant.

Written by the indexing model from the issue text.