fix(governance): audit merged PRs after branch cleanup

tests/test_governance.py

@@ -23,6 +23,8 @@ from audit_gitea_coordination import (
     parse_datetime,
     parse_write_paths,
     select_latest_claim,
+    RemoteTask,
+    validate_pull_request,
 )
 from setup_gitea_labels import LABELS, NoRedirect, build_plan
 from test_gitea_claim_race import PROBE_PREFIX, new_probe_branch
@@ -180,6 +182,31 @@ class OfflineRuleTests(unittest.TestCase):
 
 
 class GiteaHelperTests(unittest.TestCase):
+    def test_merged_pr_accepts_gitea_deleted_branch_ref(self) -> None:
+        sha = "a" * 40
+        task = RemoteTask(
+            number=1,
+            task_id="T-123",
+            state="closed",
+            status="status/done",
+            labels={"status/done"},
+            body="",
+            work_branch="agent/worker-1/T-123",
+            context_ref=sha,
+            write_paths=["docs/tasks/T-123.md"],
+        )
+        pr = {
+            "merged": True,
+            "head": {"ref": "refs/pull/1/head"},
+            "body": (
+                "Closes #1\n"
+                "task_file: docs/tasks/T-123.md\n"
+                f"context_ref: {sha}\n"
+                "work_branch: agent/worker-1/T-123\n"
+            ),
+        }
+        self.assertEqual([], validate_pull_request(pr, task))
+
     def test_waiting_status_is_not_claimable_or_active(self) -> None:
         self.assertIn("status/waiting", STATUS_LABELS)
         self.assertNotIn("status/waiting", READY_OR_ACTIVE_LABELS)