Function socket_path_for_session 

pub fn socket_path_for_session(session_id: &str) -> String

Returns the Unix domain socket path for a session. Sockets live in the registry dir — $SYNAPS_RUNTIME_DIR when set (e.g. /run/user/<uid>/synaps), otherwise $SYNAPS_BASE_DIR/run (default ~/.synaps-cli/run/) — which is user-owned and mode 0700, avoiding /tmp symlink squatting and TOCTOU races.