chore: stable job name for branch protection (#883)

adopts https://github.com/bazel-contrib/rules-template/pull/124

.github/workflows/ci.yaml

@@ -138,3 +138,24 @@ jobs:
       - name: Verify bcr patches
         if: matrix.folder == '.' && matrix.bzlmod == '1' && matrix.os == 'ubuntu' && matrix.bazel-version.major != '6'
         run: patch --dry-run -p1 < .bcr/patches/*.patch
+
+  # For branch protection settings, this job provides a "stable" name that can be used to gate PR merges
+  # on "all matrix jobs were successful".
+  conclusion:
+    needs: test
+    runs-on: ubuntu-latest
+    if: always()
+    steps:
+      - uses: technote-space/workflow-conclusion-action@45ce8e0eb155657ab8ccf346ade734257fd196a5 # v3.0.3
+
+      # Note: possible conclusion values:
+      # https://github.com/technote-space/workflow-conclusion-action/blob/main/src/constant.ts
+      - name: report success
+        if: ${{ env.WORKFLOW_CONCLUSION == 'success' }}
+        working-directory: /tmp
+        run: echo ${{ env.WORKFLOW_CONCLUSION }} && exit 0
+
+      - name: report failure
+        if: ${{ env.WORKFLOW_CONCLUSION == 'failure' }}
+        working-directory: /tmp
+        run: echo ${{ env.WORKFLOW_CONCLUSION }} && exit 1