Add final-report mutation ledger verifier (#331)

Introduce assess_mutation_ledger_report so reviewer final reports cannot
claim no file edits when the action log records performed mutations.

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

tests/test_mutation_ledger_report.py

@@ -0,0 +1,102 @@
+"""Tests for final-report mutation ledger verifier (#331)."""
+import sys
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from review_proofs import assess_mutation_ledger_report  # noqa: E402
+
+
+class TestMutationLedgerReport(unittest.TestCase):
+    def test_none_claim_with_performed_edit_blocks(self):
+        report = (
+            "Review decision: request_changes.\n"
+            "File edits by reviewer: none\n"
+        )
+        action_log = [
+            {"action": "Edited", "path": "walkthrough.md", "tracked": False},
+        ]
+        result = assess_mutation_ledger_report(report, action_log=action_log)
+        self.assertFalse(result["proven"])
+        self.assertTrue(result["file_edits_claimed_none"])
+
+    def test_reported_edit_passes(self):
+        report = (
+            "File edits by reviewer: Edited walkthrough.md (untracked)\n"
+            "Mutation ledger: Edited walkthrough.md untracked in review worktree\n"
+        )
+        action_log = [
+            {
+                "action": "Edited",
+                "path": "walkthrough.md",
+                "tracked": False,
+                "in_repo": True,
+            },
+        ]
+        result = assess_mutation_ledger_report(
+            report,
+            action_log=action_log,
+            walkthrough_explicitly_requested=True,
+        )
+        self.assertTrue(result["proven"])
+
+    def test_unreported_mutation_blocks(self):
+        report = "File edits by reviewer: none\n"
+        action_log = [{"action": "Wrote", "path": "/tmp/review-notes.txt"}]
+        result = assess_mutation_ledger_report(report, action_log=action_log)
+        self.assertFalse(result["proven"])
+        self.assertIn("/tmp/review-notes.txt", result["unreported_paths"])
+
+    def test_outside_repo_requires_label(self):
+        report = (
+            "File edits by reviewer: Wrote /tmp/review-notes.txt\n"
+        )
+        action_log = [
+            {
+                "action": "Wrote",
+                "path": "/tmp/review-notes.txt",
+                "outside_repo": True,
+            },
+        ]
+        result = assess_mutation_ledger_report(report, action_log=action_log)
+        self.assertFalse(result["proven"])
+        self.assertIn("outside repo", " ".join(result["reasons"]).lower())
+
+    def test_gated_rejection_excluded_from_performed(self):
+        report = "File edits by reviewer: none\nRejected gated calls: submit_pr_review blocked\n"
+        action_log = [
+            {
+                "action": "Edited",
+                "path": "walkthrough.md",
+                "performed": False,
+                "gated_rejected": True,
+            },
+        ]
+        result = assess_mutation_ledger_report(report, action_log=action_log)
+        self.assertTrue(result["proven"])
+        self.assertEqual(result["performed_mutations"], [])
+
+    def test_post_status_artifact_requires_final_git_status(self):
+        report = (
+            "File edits by reviewer: Created scratch/notes.md (untracked)\n"
+        )
+        action_log = [
+            {
+                "action": "Created",
+                "path": "scratch/notes.md",
+                "tracked": False,
+                "after_git_status": True,
+            },
+        ]
+        result = assess_mutation_ledger_report(
+            report,
+            action_log=action_log,
+            final_git_status_reported=False,
+        )
+        self.assertFalse(result["proven"])
+        self.assertIn("final git status", " ".join(result["reasons"]).lower())
+
+
+if __name__ == "__main__":
+    unittest.main()