feat: require post-merge cleanup safety-gate proof in reviewer reports (Closes #402)

Adds post_merge_cleanup_proof validation so cleanup claims must carry the
branch deletion and worktree removal checklists, or report CLEANUP_SKIPPED
with an exact blocker.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

tests/test_post_merge_cleanup_proof.py

@@ -0,0 +1,169 @@
+"""Tests for post-merge cleanup proof enforcement (#402)."""
+import sys
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from final_report_validator import assess_final_report_validator  # noqa: E402
+from post_merge_cleanup_proof import (  # noqa: E402
+    CLEANUP_SKIPPED,
+    assess_post_merge_cleanup_proof,
+)
+
+MERGE_SHA = "a" * 40
+HEAD_BRANCH = "feat/issue-274-branches-only-worktrees"
+WORKTREE = "branches/review-pr374-conflicts"
+
+
+def _full_remote_cleanup_report(**overrides):
+    fields = {
+        "Task": "review PR #374",
+        "Merge result": "merged",
+        "Merge commit SHA": MERGE_SHA,
+        "Cleanup status": "remote branch deleted",
+        "Delete-branch capability resolved": "gitea.branch.delete allowed via delete_branch task",
+        "Merged PR head branch": HEAD_BRANCH,
+        "Deleted branch": HEAD_BRANCH,
+        "Branch protection": "none",
+        "Open PR inventory proof": "no other open PR references branch (inventory complete)",
+        "Active heartbeat/claim/lease": "none",
+        "Cleanup mutations": "gitea_delete_branch on remote head branch",
+    }
+    fields.update(overrides)
+    lines = ["## Controller Handoff", ""]
+    lines.extend(f"- {key}: {value}" for key, value in fields.items())
+    return "\n".join(lines)
+
+
+def _full_worktree_cleanup_report(**overrides):
+    fields = {
+        "Task": "review PR #374",
+        "Merge result": "merged",
+        "Cleanup status": "local worktree removed",
+        "Removed worktree path": WORKTREE,
+        "Pre-removal tracked state": "clean",
+        "Pre-removal untracked state": "clean",
+        "Git worktree list after removal": "only main checkout listed",
+        "Cleanup mutations": "git worktree remove on session-owned review worktree",
+    }
+    fields.update(overrides)
+    lines = ["## Controller Handoff", ""]
+    lines.extend(f"- {key}: {value}" for key, value in fields.items())
+    return "\n".join(lines)
+
+
+class TestPostMergeCleanupProof(unittest.TestCase):
+    def test_no_cleanup_claim_passes(self):
+        report = "## Controller Handoff\n- Task: review PR #1\n- Merge result: merged"
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertFalse(result["block"])
+
+    def test_missing_capability_proof_blocked(self):
+        report = _full_remote_cleanup_report(
+            **{"Delete-branch capability resolved": "delete succeeded"}
+        )
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+        self.assertTrue(any("capability" in r.lower() for r in result["reasons"]))
+
+    def test_unmerged_pr_blocked(self):
+        report = _full_remote_cleanup_report(**{"Merge result": "not merged"})
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+        self.assertTrue(any("merge result" in r.lower() for r in result["reasons"]))
+
+    def test_wrong_branch_blocked(self):
+        report = _full_remote_cleanup_report(
+            **{"Deleted branch": "feat/other-branch"}
+        )
+        report += "\nDeleted branch does not match merged PR head branch"
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+
+    def test_protected_branch_blocked(self):
+        report = _full_remote_cleanup_report(**{"Branch protection": "enabled"})
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+
+    def test_open_pr_reference_blocked(self):
+        report = _full_remote_cleanup_report(
+            **{"Open PR inventory proof": "PR #999 still references branch"}
+        )
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+
+    def test_active_claim_blocked(self):
+        report = _full_remote_cleanup_report(
+            **{"Active heartbeat/claim/lease": "status:in-progress on linked issue"}
+        )
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+
+    def test_dirty_worktree_blocked(self):
+        report = _full_worktree_cleanup_report(
+            **{"Pre-removal tracked state": "dirty"}
+        )
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+        self.assertTrue(any("tracked" in r.lower() for r in result["reasons"]))
+
+    def test_foreign_worktree_blocked(self):
+        report = _full_worktree_cleanup_report(
+            **{"Removed worktree path": "/tmp/foreign-worktree"}
+        )
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+        self.assertTrue(any("branches/" in r.lower() for r in result["reasons"]))
+
+    def test_cleanup_skipped_with_blocker_passes(self):
+        report = "\n".join([
+            "## Controller Handoff",
+            "- Cleanup outcome: CLEANUP_SKIPPED",
+            "- Cleanup blocker: gitea.branch.delete capability not resolved in active profile",
+        ])
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertFalse(result["block"])
+        self.assertEqual(result["outcome"], CLEANUP_SKIPPED)
+
+    def test_cleanup_skipped_without_blocker_blocked(self):
+        report = "## Controller Handoff\n- Cleanup outcome: CLEANUP_SKIPPED"
+        result = assess_post_merge_cleanup_proof(report)
+        self.assertTrue(result["block"])
+
+    def test_full_remote_cleanup_passes(self):
+        result = assess_post_merge_cleanup_proof(_full_remote_cleanup_report())
+        self.assertFalse(result["block"])
+        self.assertTrue(result["remote_delete_claimed"])
+
+    def test_full_worktree_cleanup_passes(self):
+        result = assess_post_merge_cleanup_proof(_full_worktree_cleanup_report())
+        self.assertFalse(result["block"])
+        self.assertTrue(result["worktree_remove_claimed"])
+
+    def test_validator_integration_blocks_unproven_delete(self):
+        report = (
+            "## Controller Handoff\n"
+            "- Cleanup mutations: gitea_delete_branch deleted remote branch\n"
+        )
+        result = assess_final_report_validator(report, task_kind="review_pr")
+        self.assertTrue(result["blocked"])
+        rule_ids = [f["rule_id"] for f in result["findings"]]
+        self.assertIn("reviewer.post_merge_cleanup_proof", rule_ids)
+
+    def test_validator_integration_allows_skipped(self):
+        report = "\n".join([
+            "## Controller Handoff",
+            "- Cleanup outcome: CLEANUP_SKIPPED",
+            "- Cleanup blocker: branch still referenced by open PR #414",
+        ])
+        result = assess_final_report_validator(report, task_kind="review_pr")
+        cleanup_findings = [
+            f for f in result["findings"]
+            if f["rule_id"] == "reviewer.post_merge_cleanup_proof"
+        ]
+        self.assertEqual(cleanup_findings, [])
+
+
+if __name__ == "__main__":
+    unittest.main()