Function spawn_tracked_pid 

pub fn spawn_tracked_pid(
    reap_tx: &Sender<Reaped>,
    spawn_fn: impl FnOnce() -> Result<Child>,
) -> Result<Child>

spawn_tracked for a plain std::process::Child — an instance-tier child, which is a full daemon with no control channel. Same contract: the fork happens under the routes lock so the reaper can never waitpid the pid before it is registered.