feat: reject contradictory reviewer handoff ledgers (Closes #501)

Add reviewer_handoff_consistency validation for narrative vs mutation
ledger contradictions, wire it into review_pr final-report rules, and
document the blocked-review handoff template.

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

final_report_validator.py

@@ -12,6 +12,7 @@ import re
 from typing import Any, Callable
 
 import issue_lock_provenance
+import reviewer_handoff_consistency
 from review_proofs import (
     HANDOFF_HEADING,
     assess_controller_handoff,
@@ -956,6 +957,25 @@ def _rule_reviewer_validation_structured(
     )
 
 
+def _rule_reviewer_handoff_consistency(report_text: str) -> list[dict[str, str]]:
+    result = reviewer_handoff_consistency.assess_reviewer_handoff_consistency(
+        report_text
+    )
+    if result.get("proven"):
+        return []
+    return _findings_from_reasons(
+        "reviewer.handoff_consistency",
+        result.get("reasons") or [],
+        field="Review mutations",
+        severity="block",
+        safe_next_action=(
+            "rewrite reviewer handoff so narrative claims match the mutation "
+            "ledger; use the blocked-review handoff template when submission "
+            "was rejected"
+        ),
+    )
+
+
 def _rule_reviewer_mutation_ledger(
     report_text: str,
     *,
@@ -1069,6 +1089,7 @@ _RULES_BY_TASK: dict[str, list[Callable[..., list[dict[str, str]]]]] = {
         _rule_reviewer_already_landed_eligible,
         _rule_reviewer_already_landed_state,
         _rule_reviewer_target_branch_freshness,
+        _rule_reviewer_handoff_consistency,
         _rule_reviewer_mutation_ledger,
         _rule_reviewer_review_mutation,
         _rule_reviewer_stale_head_proof,