Air-Gapped Implementation 4 — Nodepool static node — VM3 runner

Describe provider configuration, label sizing, and image build process for nodes that run Kolla builds.

For Environment B, the runner is a static Ubuntu Jammy container on VM3 with Docker socket access. Keep the node definition in etc_nodepool/nodepool.yaml, ensure the public key matches the runner's authorized_keys, and pin labels so Zuul jobs always target the controlled runner container. Document the image provenance and the offline steps required to refresh the runner image alongside the Zuul compose updates.