fix(review): cross-PR decision-lock isolation and recovery diagnosis (Closes #693)

Prevent foreign open-PR terminals on the durable review-decision lock from
blocking fresh formal reviews. Scope correction authorization to the named
prior review's PR/head, add read-only diagnosis with exact next_action and
durable handoff payloads, require thread-visible correction audits, and
cover the PR #688 → #692 recovery sequence in regression tests.

tests/test_mcp_server.py

@@ -2540,15 +2540,18 @@ class TestSubmitPrReview(unittest.TestCase):
         lock = _load_review_decision_lock() or {}
         lock["live_mutations"] = [{"pr_number": 8, "action": "approve", "review_id": 42, "review_state": "approve"}]
         _save_review_decision_lock(lock)
-        r = gitea_authorize_review_correction(
-            prior_review_id=42,
-            prior_review_state="approve",
-            reason="typo",
-            operator_authorized=True,
-        )
+        with patch("mcp_server.api_request", return_value={"id": 9001}):
+            r = gitea_authorize_review_correction(
+                prior_review_id=42,
+                prior_review_state="approve",
+                reason="typo",
+                operator_authorized=True,
+                target_pr_number=8,
+            )
         self.assertTrue(r["authorized"])
         lock = _load_review_decision_lock()
         self.assertTrue(lock["correction_authorized"])
+        self.assertEqual(lock["correction_pr_number"], 8)
 
     def test_authorize_review_correction_mismatch(self):
         from mcp_server import _load_review_decision_lock, _save_review_decision_lock
@@ -2562,6 +2565,7 @@ class TestSubmitPrReview(unittest.TestCase):
             prior_review_state="approve",
             reason="typo",
             operator_authorized=True,
+            target_pr_number=8,
         )
         self.assertFalse(r["authorized"])
         self.assertTrue(any("prior review ID" in x for x in r["reasons"]))
@@ -2572,10 +2576,22 @@ class TestSubmitPrReview(unittest.TestCase):
             prior_review_state="request_changes",
             reason="typo",
             operator_authorized=True,
+            target_pr_number=8,
         )
         self.assertFalse(r["authorized"])
         self.assertTrue(any("prior review state" in x for x in r["reasons"]))
 
+        # Cross-PR unlock refused (#693)
+        r = gitea_authorize_review_correction(
+            prior_review_id=42,
+            prior_review_state="approve",
+            reason="unlock other pr",
+            operator_authorized=True,
+            target_pr_number=692,
+        )
+        self.assertFalse(r["authorized"])
+        self.assertTrue(any("different PR" in x for x in r["reasons"]))
+
     def test_authorize_review_correction_requires_operator_auth(self):
         from mcp_server import _load_review_decision_lock, _save_review_decision_lock
         lock = _load_review_decision_lock() or {}
@@ -2588,6 +2604,7 @@ class TestSubmitPrReview(unittest.TestCase):
             prior_review_state="approve",
             reason="typo",
             operator_authorized=False,
+            target_pr_number=8,
         )
         self.assertFalse(r["authorized"])
         self.assertTrue(any("operator authorization" in x for x in r["reasons"]))
@@ -2645,6 +2662,7 @@ class TestSubmitPrReview(unittest.TestCase):
                     prior_review_state="approve",
                     reason="operator approved correcting mistaken approve",
                     operator_authorized=True,
+                    target_pr_number=8,
                 )
                 _mark_request_changes_ready(remote="prgs")
                 second = gitea_submit_pr_review(