Disabling SSH root login (PermitRootLogin no) severs Clusev's OWN access when it
connects AS root — afterwards neither key nor password reaches root. The
password-auth toggle already guards against self-lockout; the root toggle did not.
Refuse to disable root login while the active credential's username is root, with a
clear message: add a non-root sudo user + key and switch Clusev to it first.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Auth success alone does not prove the server can run commands (a server that
authenticates but rejects exec channels would be accepted, yet every fleet
operation runs commands). The probe now echoes a unique marker and requires it
in the output — proving exec works, while still tolerating servers that omit
the optional exit-status packet.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>