ci: fix runner labels + CoreDNS rewrite + cleanup

- Runners use public images (code.forgejo.org/forgejo/runner:6)
- Labels pull from Docker Hub: golang:1.26, node:22, rust:1-bookworm
- Add CoreDNS api.riotpiao.com rewrite
- Fix runner re-registration to keep labels in sync
- Add unified CI pattern docs to CLAUDE.example.md
- Remove dead .forgejo/ workflow dir (Forgejo uses .gitea/)

k8s/infra/forgejo-runner/values-node.yaml

@@ -2,9 +2,12 @@
 # runner instance. Only runner.name and runner.labels differ -- everything
 # else (image, dind, persistence, tolerations, nodeSelector) is shared.
 #
-# node:22-bookworm ships Node natively. Docker client installed via workflow step if needed.
-# (homelab has no CI; custom runner images built manually if desired)
+# Label image: node:22-bookworm — Debian, root, apt-get, Node.js, npm, git.
+# Install docker in workflow steps as needed.
 runner:
+  image:
+    repository: code.forgejo.org/forgejo/runner
+    tag: "6"
   name: node-runner
   labels: "node:docker://node:22-bookworm"