Bug: AddKnownHost wrote raw SSH wire-protocol bytes directly to
known_hosts instead of the OpenSSH authorized-key one-line format.
This produced garbage entries that would break SSH verification
for newly added machines.
Fix: ssh.ParsePublicKey(keyData) + ssh.MarshalAuthorizedKey() to
produce canonical hostkey lines: hostname ssh-ed25519 AAAAB3...xn3c=
darroyo
6d16797c4f