👷 ci: validate PR description headings

Author: zrr1999

.github/pull_request_template.md

@@ -0,0 +1,11 @@
+## Summary
+
+Describe the change in 2-5 bullets.
+
+## Validation
+
+List the commands, checks, or CI evidence that validate this PR.
+
+## Notes
+
+Add any context that helps reviewers focus on the important details.

.github/workflows/ci-pr-checks.yml

@@ -23,3 +23,50 @@ jobs:
         uses: zrr1999/zendev-actions/validate-title@9013ad848b32d287d0258fdbc9f51e350b8eca33
         with:
           text: ${{ github.event.pull_request.title }}
+
+  description:
+    name: PR description
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Check PR description headings
+        env:
+          GITHUB_EVENT_PATH: ${{ github.event_path }}
+        run: |
+          python - <<'PY'
+          import json
+          import os
+          import re
+          import sys
+          from pathlib import Path
+
+          def extract_h2_headings(text: str) -> list[str]:
+              in_fence = False
+              headings = []
+              for line in text.splitlines():
+                  stripped = line.strip()
+                  if stripped.startswith("```"):
+                      in_fence = not in_fence
+                      continue
+                  if in_fence:
+                      continue
+                  if re.match(r"^##\s+\S", stripped):
+                      headings.append(re.sub(r"^##\s+", "", stripped))
+              return headings
+
+          payload = json.loads(Path(os.environ["GITHUB_EVENT_PATH"]).read_text(encoding="utf-8"))
+          body = (payload.get("pull_request") or {}).get("body") or ""
+          template = Path(".github/pull_request_template.md").read_text(encoding="utf-8")
+
+          expected = extract_h2_headings(template)
+          actual = extract_h2_headings(body)
+
+          if actual != expected:
+              print("PR description headings do not match the repository template.", file=sys.stderr)
+              print(f"Expected headings: {expected}", file=sys.stderr)
+              print(f"Actual headings:   {actual}", file=sys.stderr)
+              raise SystemExit(1)
+
+          print("PR description headings match the repository template.")
+          PY