Wrap first-use SSH and SCP multiplexed commands with a lock to avoid racing while the control socket is created. Also detect native OpenSSH mux master process names during stale connection cleanup and cover both orphaned and duplicate mux processes with tests.
Remove explicit SSH master pre-warming and lock handling so OpenSSH manages ControlMaster creation lazily from real ssh/scp commands. Add cleanup for duplicate mux processes and update coverage around mux command options and stale process cleanup.
Serialize multiplexed SSH master creation per server to avoid concurrent workers spawning orphaned processes. Enable scheduled cleanup for stale mux connections and add guarded orphan process reaping with tests.
