Function bind_socket_with_recovery 

pub(crate) fn bind_socket_with_recovery(
    socket_path: &str,
    data_dir: &Path,
    dir_hash: &str,
    channel: &str,
) -> UnixListener

Bind the launcher’s IPC socket with single-instance enforcement + crash-safe stale-socket recovery, serialized across concurrent launchers via flock(2).

Returns a bound UnixListener on success. Calls std::process::exit on:

• second-instance detection (exit code 0)
• a hard bind failure that isn’t EADDRINUSE (exit code 2)
• unable to acquire the recovery lock (exit code 2)

Why the lockfile (codex P1 + reagent P1 on PR #1288): see the call- site comment. Two-launcher concurrent stale-cleanup would otherwise produce two live launchers for one data dir.