Function run_ud_pump 

pub async fn run_ud_pump(
    core: Arc<Mutex<UdCore>>,
    emitter: Arc<Emitter>,
    rx: AsyncReceiver<IncomingMessage>,
    cancel: CancellationToken,
)

Runs the user data event pump until cancel fires or the frame channel closes.

Same loop as run_md_pump, with the user data core (order status, fills, portfolio).