fix(governance): audit merged PRs after branch cleanup

scripts/audit_gitea_coordination.py

@@ -243,13 +243,25 @@ def validate_pull_request(
     pr: dict[str, Any], task: RemoteTask
 ) -> list[AuditFinding]:
     findings: list[AuditFinding] = []
-    if not task.work_branch or pull_request_head(pr) != task.work_branch:
+    body = pr.get("body")
+    body = body if isinstance(body, str) else ""
+    head = pull_request_head(pr)
+    head_matches = bool(task.work_branch) and head == task.work_branch
+    if (
+        not head_matches
+        and bool(pr.get("merged"))
+        and re.fullmatch(r"refs/pull/\d+/head", head)
+        and bool(task.work_branch)
+        and task.work_branch in body
+    ):
+        # Gitea rewrites head.ref after a merged source branch is deleted. The
+        # immutable PR body still records the claimed work branch.
+        head_matches = True
+    if not head_matches:
         findings.append(
             AuditFinding(task.number, "pull-request", "PR head 与 claim 工作分支不一致。")
         )
-    body = pr.get("body")
-    body = body if isinstance(body, str) else ""
-    required_values = [f"docs/tasks/{task.task_id}.md"]
+    required_values = [f"docs/tasks/{task.task_id}.md", task.work_branch or ""]
     if task.context_ref:
         required_values.append(task.context_ref)
     required_values.extend(task.write_paths or [])