rlmesh::ext::remove_stale_socket
Remove a leftover Unix-domain socket file before binding.
fn remove_stale_socket(path: &std::path::Path) -> Result<()>bind(2) returns EADDRINUSE whenever the socket path already exists on
disk, regardless of whether anything is listening, so a socket left by a
crashed server must be unlinked before we rebind. We probe first to avoid
stealing the address from a live server: a successful connect means the
socket is live and we refuse to bind, and only a ConnectionRefused probe
is treated as stale and unlinked. Any other connect failure (e.g. permission
denied) cannot prove the socket is dead, so we report it rather than risk
unlinking a socket still in use. Non-socket files are left for bind to
reject.