Descriptor.HostFingerprint (SHA256, non-secret), captured at provision via an
x/crypto/ssh keyscan (SSHHostKeyScanner — dials :23, grabs the host key from the
handshake, no ssh binary). Fail-closed: nil scanner or scan failure → error (don't
serve a descriptor the controller can't verify). Pairs with controller v0.106.0
which re-scans + refuses on mismatch (no blind TOFU).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6
