ci: publish the hub image to GHCR, and verify it actually starts

.github/workflows/hub-ci.yml

@@ -5,6 +5,12 @@ on:
   push:
     branches: [main, "feat/**", "fix/**", harness-integration]
 
+# A newer push supersedes any older run for the same branch. In particular,
+# an older main build must not finish later and move `latest` backwards.
+concurrency:
+  group: hub-ci-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   # The fast deterministic suite: levels/config parsing, validator, prompts,
   # temporal, KB, roles, and the /v1 OpenAI-compat contract (test_bridge) that
@@ -37,5 +43,100 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      # HUB_BUILD_REVISION must be the real commit: validate_config() rejects
+      # the Dockerfile's "unknown" default, so an image built without it builds
+      # fine and then refuses to start.
       - name: Build image
-        run: docker build .
+        run: |
+          docker build --build-arg HUB_BUILD_REVISION="${GITHUB_SHA}" -t hub-ci-candidate .
+
+      # Building is not evidence the image runs: validate_config() executes at
+      # import, so a container that starts and answers /health is what proves
+      # the packaged configuration is actually serviceable.
+      - name: Verify the image starts and serves /health
+        run: |
+          docker run -d --name hub-smoke -p 8080:8080 hub-ci-candidate
+          for i in $(seq 1 30); do
+            if curl -fsS http://localhost:8080/health >/dev/null 2>&1; then
+              echo "healthy after ${i}s"
+              docker rm -f hub-smoke >/dev/null
+              exit 0
+            fi
+            sleep 1
+          done
+          echo "image never served /health:" >&2
+          docker logs hub-smoke >&2
+          docker rm -f hub-smoke >/dev/null
+          exit 1
+
+      # Preserve the tested bytes for the separately permissioned publish job.
+      # Pull requests prove the build and startup path but do not upload or push.
+      - name: Export the tested image
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: docker save --output /tmp/hub-ci-candidate.tar hub-ci-candidate
+
+      - name: Transfer the tested image to the publish job
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        uses: actions/upload-artifact@v4
+        with:
+          name: hub-ci-candidate-${{ github.sha }}
+          path: /tmp/hub-ci-candidate.tar
+          retention-days: 1
+          if-no-files-found: error
+
+  # Only reviewed main commits may publish. This job receives the exact image
+  # that passed /health; it never rebuilds the source tree.
+  publish:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    needs: [unit-and-contract, docker-build]
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    outputs:
+      published-image: ${{ steps.publish.outputs.image }}
+    steps:
+      - name: Download the tested image
+        uses: actions/download-artifact@v4
+        with:
+          name: hub-ci-candidate-${{ github.sha }}
+          path: /tmp
+
+      - name: Load and verify the tested image
+        run: |
+          docker load --input /tmp/hub-ci-candidate.tar
+          revision="$(docker image inspect --format \
+            '{{index .Config.Labels "org.opencontainers.image.revision"}}' \
+            hub-ci-candidate)"
+          test "${revision}" = "${GITHUB_SHA}"
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Publish the exact local image that passed /health. Tags are convenient
+      # lookup names and can move; deployments must pin the recorded digest.
+      - name: Publish the tested image and record its immutable digest
+        id: publish
+        env:
+          IMAGE_NAME: ghcr.io/${{ github.repository }}
+        run: |
+          docker tag hub-ci-candidate "${IMAGE_NAME}:${GITHUB_SHA}"
+          docker tag hub-ci-candidate "${IMAGE_NAME}:latest"
+          docker push "${IMAGE_NAME}:${GITHUB_SHA}"
+          docker push "${IMAGE_NAME}:latest"
+
+          digest="$(docker buildx imagetools inspect \
+            "${IMAGE_NAME}:${GITHUB_SHA}" --format '{{.Manifest.Digest}}')"
+          case "${digest}" in
+            sha256:????????????????????????????????????????????????????????????????) ;;
+            *) echo "Could not resolve the published manifest digest: ${digest}" >&2; exit 1 ;;
+          esac
+
+          immutable_image="${IMAGE_NAME}@${digest}"
+          echo "image=${immutable_image}" >> "${GITHUB_OUTPUT}"
+          echo "### Published tested Hub image" >> "${GITHUB_STEP_SUMMARY}"
+          echo "\`${immutable_image}\`" >> "${GITHUB_STEP_SUMMARY}"