Client.close

Close owned control clients and descriptors on the owning domain. Later calls retain the original cleanup result, including failure. Each owned helper gets 200 ms of TERM grace, followed by KILL if needed and reaping. This is not a whole-client deadline or a bound on uninterruptible kernel work. No signal targets the daemon. tmux's exit-unattached and exit-empty policies can end the daemon after its clients or sessions disappear.