Phase 5: scaffold Crucible (sow-tools) — dispatcher + builder shims, container, PR-first CI, fail-closed (D11, D19).

.gitea/workflows/build-image.yml

@@ -0,0 +1,40 @@
+# Build the Crucible image. PR-first (D7): PRs build only; push to main also
+# publishes registry.westgate.pw/sow/crucible:<git-sha>. Never a mutable tag.
+name: build-image
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+env:
+  REGISTRY: registry.westgate.pw
+  IMAGE: sow/crucible
+
+jobs:
+  build-image:
+    runs-on: docker
+    steps:
+      - uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+
+      - name: Resolve tag
+        id: tag
+        run: echo "sha=$(git rev-parse --short=12 HEAD)" >> "$GITHUB_OUTPUT"
+
+      - name: Build image
+        run: |
+          docker build \
+            --build-arg GIT_SHA=${{ steps.tag.outputs.sha }} \
+            -f docker/Dockerfile \
+            -t ${REGISTRY}/${IMAGE}:${{ steps.tag.outputs.sha }} .
+
+      # Publish only on main (post-merge). PRs verify the build but never push.
+      - name: Publish image
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        env:
+          REGISTRY_USER: ${{ secrets.REGISTRY_USER }}
+          REGISTRY_PASSWORD: ${{ secrets.REGISTRY_PASSWORD }}
+        run: |
+          echo "${REGISTRY_PASSWORD}" | docker login "${REGISTRY}" -u "${REGISTRY_USER}" --password-stdin
+          docker push ${REGISTRY}/${IMAGE}:${{ steps.tag.outputs.sha }}