libtmux:suspend-client

Request suspension of captured terminal TARGET; return a COMMAND-OUTCOME. Tmux asks the frontend to stop with SIGTSTP. Success acknowledges the request; it does not prove process suspension. An already suspended frontend can be a no-op. Its controlling application owns resumption. CLIENT must own TARGET. Blocks under shared preflight/dispatch limits; returns no replacement. Stale or foreign targets signal STALE-TARGET; other failures retain their outcome. Preflight cannot exclude client replacement before dispatch. Never retries.