[codex] Add k3d registry support

[suin]

Summary

Adds k3d as a Kubernetes-ready distribution alongside kind, including registry detection and restore-time registry handling.

Changes

• Add k8s: kind|k3d / --k8s=kind|k3d configuration and CLI flow.
• Detect k3d API server endpoints through the k3d load balancer container.
• Detect k3d local registries and print REGISTRY for the restored VM Docker daemon.
• Update local-registry-hosting so tools such as Tilt can use local registry auto-detection.
• Add k3d registry E2E coverage.
• Add examples/k3d and examples/tilt samples.
• Update README with kind, k3d, and Tilt user guides.

Impact

Users can now choose k3d for spind Kubernetes-ready environments and use a k3d local registry from the DOCKER_HOST printed by spind. Tilt users can rely on k3d local registry auto-detection without adding default_registry() to the Tiltfile.

Validation

• task check
• task e2e
• bunx oxfmt --check .
• Manual ../../bin/spind up from examples/k3d after fixing the k3d sample readiness wait