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]>

conformance/versions.env

@@ -40,32 +40,29 @@ PYTHON_MIN="3.9"
 #   gitea.home.keithjackson.dev/home-network/conformance-runner@sha256:*
 # Any other path, and any TAG reference, is DENIED at admission. Do not "tidy" these values.
 CONFORMANCE_RUNNER_IMAGE_REPO="gitea.home.keithjackson.dev/home-network/conformance-runner"
-# Build handle only. Admission never sees the tag; a Job must reference the digest.
+# Local build handle only. Admission never sees the tag; a Job must reference the digest.
+# CI publishes under `sha-<commit>` and `main` instead (.gitea/workflows/images.yaml).
 CONFORMANCE_RUNNER_IMAGE_TAG="chainsaw0.2.12-kubectl1.36.4-fc44"
 #
 # ############################################################################
-# # DIGEST DELIBERATELY EMPTY — THE IMAGE HAS NOT BEEN PUBLISHED YET.        #
+# # THE DIGEST IS WRITTEN BY RENOVATE, NOT BY HAND.                          #
 # ############################################################################
-# The image has been BUILT and its toolchain verified locally (non-root uid 65532,
-# read-only rootfs: bash 5.3.9, Python 3.14.7, git 2.55.0, kubectl v1.36.4, chainsaw 0.2.12,
-# and `./run.sh --layer l2 --no-cluster` completing with rc 0). It has NOT been pushed:
-# pushing needs a registry credential, and publishing the artifact a fail-closed security
-# boundary then trusts is an OPERATOR action, not an agent's.
+# CI builds and verifies the image (non-root uid 65532, read-only rootfs, the
+# conformance-clone refusals) and, on a push to main, publishes it and prints the digest the
+# REGISTRY returned (.gitea/workflows/images.yaml). Renovate follows the image's `main` tag
+# through the marker below and opens the pull request that moves this value. Nobody pushes
+# this image from a workstation, and nobody pastes a digest here.
 #
-# OPERATOR, to complete the pin:
-#   1. ./conformance/incluster/build-image.sh          # rebuild, verify, print the commands
-#   2. podman login gitea.home.keithjackson.dev
-#   3. podman push --digestfile /tmp/conformance-runner.digest \
-#        "${CONFORMANCE_RUNNER_IMAGE_REPO}:${CONFORMANCE_RUNNER_IMAGE_TAG}"
-#   4. Set CONFORMANCE_RUNNER_IMAGE_DIGEST below to `cat /tmp/conformance-runner.digest`
-#      — the digest the REGISTRY returned, not the local manifest digest the build printed.
-#   5. Land steps 4 in a PR (this file is GitOps input, not a live edit).
-#
-# UNTIL THEN: this is empty on purpose, NOT a placeholder to be guessed at. An empty value
-# makes any consumer that renders the Job fail visibly; a fake or stale digest would instead
-# produce an ImagePullBackOff that looks like a cluster fault. Do not invent one.
-CONFORMANCE_RUNNER_IMAGE_DIGEST=""
-CONFORMANCE_RUNNER_IMAGE="${CONFORMANCE_RUNNER_IMAGE_DIGEST:+${CONFORMANCE_RUNNER_IMAGE_REPO}@${CONFORMANCE_RUNNER_IMAGE_DIGEST}}"
+# ALL-ZERO UNTIL THE FIRST PUBLISH. Before 2026-10-29 this was EMPTY, so that a consumer
+# rendering the Job would fail visibly. It is now the same impossible all-zero digest
+# platform/pm-agent/ uses, because Renovate can only replace a digest that is there to match.
+# A consumer MUST treat the all-zero value as "not published" (no consumer exists yet: the
+# L2/L3 trigger is unwired, docs/plans/l2-l3-conformance-ci-wiring.md). Note also that
+# chainsaw-job.yaml's @@CONFORMANCE_RUNNER_IMAGE_DIGEST@@ takes the 64 hex digits WITHOUT the
+# `sha256:` prefix this value carries — the trigger must strip it.
+# renovate-digest: image=gitea.home.keithjackson.dev/home-network/conformance-runner tag=main
+CONFORMANCE_RUNNER_IMAGE_DIGEST="sha256:0000000000000000000000000000000000000000000000000000000000000000"
+CONFORMANCE_RUNNER_IMAGE="${CONFORMANCE_RUNNER_IMAGE_REPO}@${CONFORMANCE_RUNNER_IMAGE_DIGEST}"
 #
 # AFTERWARDS, TIGHTEN THE BOUNDARY: the header of conformance-trigger-job-shape.yaml asks for
 # its `@sha256:*` wildcard to be replaced with the LITERAL digest once the image exists —