Function service_reachable 

pub fn service_reachable(data_dir: &Path, dir_hash: &str) -> bool

Is the background service actually reachable right now?

Deliberately the same question forward_host_cmd has to answer — port file readable AND the host’s IPC port accepting a connection — because that is what the indicator should mean: “would Open work if you clicked it?”. Checking only that the port file exists would keep claiming “running” after a host crash, since the file outlives a hard exit (see lib.rs, which removes it only on a clean run_message_loop return).