New local-API POST /controller/swap (+ GET /controller/swap/status), withGuest-
scoped: the agent records the previous image, confirms the target is present,
rewrites /etc/felhom-controller-image, restarts felhom-controller-bootstrap.service,
verifies the new controller is healthy (docker inspect, <=90s), and ROLLS BACK to
the previous image if not. Single-flight per guest; strict image-ref validation;
crash-safety state file. GuestBinder.GuestExec is the pct-exec seam.
--selftest=controller-swap exercises it directly.
Tests: happy/rollback-on-unhealthy(+red-proof)/image-absent/no-healthcheck/
bad-image-400/single-flight-409.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TtXesNa2LGbMmE4DNL6SE7
