Fix the Go control plane NAT path now that runtime state lives in the daemon instead of the old repo-local vm.json files.
Add a daemon-native NAT helper that derives uplink, guest IP, and TAP rules directly from VMRecord, applies the existing iptables/sysctl behavior idempotently, and removes the broken nat.sh handoff from vm.go.
Cover uplink parsing and rule generation with unit tests. Validated with go test ./... and make build; a live verify.sh --nat run installed host rules but stopped on the same guest SSH-readiness issue seen in the plain smoke test on this host.
