Installing the agent with one key is now all it takes to add a host.
New `join_key` config field, presented while auth_token is empty. The SSO
exchanges it for this agent's own token and the public key it must pin,
both delivered in the config frame; the agent persists them and blanks
the join key. Nothing has to be copied between two machines by hand.
PersistEnrollment rewrites only the credential lines -- line-based rather
than a YAML round-trip -- so operator comments, the capability matrix and
formatting survive. It re-reads afterwards so the credential is live
without a restart, and keeps the file 0600.
The connect URL carries ?hostname= so a self-enrolling host is named
after itself, and the agent refuses to connect at all (with a long
back-off) when it has no credential rather than presenting an empty one.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>