ci: stable required-check anchors for skippable matrix test jobs (#40772)

Co-authored-by: Claude Code <noreply@anthropic.com>

.github/workflows/superset-python-integrationtest.yml

@@ -226,3 +226,25 @@ jobs:
           verbose: true
           use_oidc: true
           slug: apache/superset
+
+  # Stable required-status-check anchor for the matrix-based test-postgres job.
+  # It is gated on change detection, so on non-Python PRs it is skipped and
+  # never produces its `test-postgres (current)` context (a job-level skip
+  # happens before matrix expansion). This always-running job reports a single
+  # context branch protection can require: it passes when test-postgres
+  # succeeded or was skipped, and fails only on a real failure.
+  test-postgres-required:
+    needs: [changes, test-postgres]
+    if: always()
+    runs-on: ubuntu-24.04
+    timeout-minutes: 5
+    steps:
+      - name: Check test-postgres result
+        env:
+          RESULT: ${{ needs.test-postgres.result }}
+        run: |
+          if [ "$RESULT" != "success" ] && [ "$RESULT" != "skipped" ]; then
+            echo "test-postgres did not pass (result: $RESULT)"
+            exit 1
+          fi
+          echo "test-postgres result: $RESULT"