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_head_scoped_review_decision_lock.py

@@ -24,6 +24,10 @@ HEAD_C = "c" * 40
 
 
 def _lock(mutations=None, correction=False, ready_pr=None, ready_head=None, ready_action=None):
+    mutations = list(mutations or [])
+    corr_pr = None
+    if correction and mutations:
+        corr_pr = mutations[-1].get("pr_number")
     return {
         "task": "review_pr",
         "remote": "prgs",
@@ -40,9 +44,11 @@ def _lock(mutations=None, correction=False, ready_pr=None, ready_head=None, read
         "ready_remote": "prgs" if ready_pr else None,
         "ready_org": "Scaled-Tech-Consulting" if ready_pr else None,
         "ready_repo": "Gitea-Tools" if ready_pr else None,
-        "live_mutations": list(mutations or []),
+        "live_mutations": mutations,
         "correction_authorized": correction,
-        "correction_reason": None,
+        "correction_reason": "test" if correction else None,
+        "correction_pr_number": corr_pr,
+        "correction_head_sha": None,
     }
 
 
@@ -174,12 +180,13 @@ class TestHardStopHeadScope(unittest.TestCase):
         self.assertTrue(reasons)
         self.assertIn("#332", reasons[0])
 
-    def test_rc_head_a_blocks_other_pr(self):
+    def test_rc_head_a_allows_other_pr_via_cross_pr_isolation(self):
+        """#693: foreign-PR terminal must not hard-stop mark_ready on another PR."""
         _seed([RC_619_HEAD_A], ready_pr=619, ready_head=HEAD_A)
         reasons = mcp_server.terminal_review_hard_stop_reasons(
             700, "mark_ready", expected_head_sha=HEAD_B
         )
-        self.assertTrue(reasons)
+        self.assertEqual(reasons, [])
 
     def test_legacy_619_ledger_allows_new_head(self):
         """PR #619-style durable lock without mutation head_sha."""