feat(images): build, verify and publish the three images in CI; Renovate carries the digests

Operator rule 2026-10-29: image creation, hosting and lifecycle belong to CI/CD, never to a
workstation build/push. Nothing had ever been pushed to the Gitea registry.

- .gitea/workflows/images.yaml + scripts/images.sh: PRs build+verify (no credential); main
  builds, verifies and pushes toolbox, agent-runner (FROM toolbox) and conformance-runner as
  sha-<commit> + main, reading the digest back from the registry. Only changed images build.
- Each image's own build-image.sh does the build and in-image verification, now engine-neutral
  (DinD: no podman-only calls, probe over stdin not a bind mount). New toolbox build-image.sh.
- Digest references carry `# renovate-digest:` markers; renovate.json5 gains a custom.regex
  manager for them. The worker Job template is deliberately untracked (it would loop).
- renovate.yaml pins renovate-version 44.167.0: the action's default (39.264.0) rejects the
  current config's managerFilePatterns, so every run would have died at CONFIG_VALIDATION.
- Push credential: REGISTRY_PUSH_TOKEN secret; the Actions token has no package scope in
  Gitea 1.24.3 (container.go Authenticate). Retention: infra/gitea/registry-retention.sh.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

infra/devcontainer/dev.sh

@@ -72,22 +72,10 @@ esac
 CLUSTER_KUBECONFIG="${REPO_ROOT}/infra/ansible/.cache/${CLUSTER}.kubeconfig"
 
 build() {
-  "$ENGINE" build \
-    --build-arg FEDORA_VERSION="$FEDORA_VERSION" \
-    --build-arg OPENTOFU_VERSION="$OPENTOFU_VERSION" \
-    --build-arg AGE_VERSION="$AGE_VERSION" \
-    --build-arg SOPS_VERSION="$SOPS_VERSION" \
-    --build-arg FLUX_VERSION="$FLUX_VERSION" \
-    --build-arg KUBECTL_VERSION="$KUBECTL_VERSION" \
-    --build-arg HELM_VERSION="$HELM_VERSION" \
-    --build-arg KYVERNO_VERSION="$KYVERNO_VERSION" \
-    --build-arg KYVERNO_JSON_VERSION="$KYVERNO_JSON_VERSION" \
-    --build-arg CHAINSAW_VERSION="$CHAINSAW_VERSION" \
-    --build-arg YAMLLINT_VERSION="$YAMLLINT_VERSION" \
-    --build-arg YQ_VERSION="$YQ_VERSION" \
-    --build-arg CHECK_JSONSCHEMA_VERSION="$CHECK_JSONSCHEMA_VERSION" \
-    --build-arg PROMTOOL_VERSION="$PROMTOOL_VERSION" \
-    -t "$IMAGE" -f "${HERE}/Containerfile" "${HERE}"
+  # The build recipe lives in build-image.sh so that CI (.gitea/workflows/images.yaml), which
+  # builds and PUBLISHES this image, and a local `dev.sh build` cannot drift apart. --no-verify
+  # keeps the local loop as fast as it always was; CI runs the verification.
+  IMAGE="$IMAGE" ENGINE="$ENGINE" "${HERE}/build-image.sh" --no-verify
 }
 
 run() {