feat: reject stale already-landed controller handoff fields (#299)

Add assess_already_landed_handoff_report verifier to block Pinned reviewed
head, Scratch worktree used, legacy Mutations/Workspace mutations None when
git fetch or other mutations occurred, and narrative/handoff drift after the
already-landed gate fires. Wire into build_final_report and review_proofs.

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

review_proofs.py

@@ -1405,6 +1405,11 @@ def build_final_report(checkout_proof, inventory, validation, contamination,
         if report_text
         else {"proven": True, "block": False, "reasons": [], "violations": []}
     )
+    already_landed_handoff = (
+        assess_already_landed_handoff_report(report_text)
+        if report_text
+        else {"proven": True, "block": False, "reasons": []}
+    )
     if baseline_validation is None and report_text:
         baseline_validation = assess_reviewer_baseline_validation_proof(
             report_text=report_text,
@@ -1561,6 +1566,11 @@ def build_final_report(checkout_proof, inventory, validation, contamination,
             "queue-status report violates loaded workflow proof gates (#339)"
         )
         downgrade_reasons.extend(queue_status_report.get("reasons", []))
+    if not already_landed_handoff.get("proven"):
+        downgrade_reasons.append(
+            "already-landed controller handoff has stale or inconsistent fields (#299)"
+        )
+        downgrade_reasons.extend(already_landed_handoff.get("reasons", []))
     if not baseline_validation.get("proven"):
         downgrade_reasons.append(
             "reviewer baseline validation proof missing or failed (#325)"
@@ -1646,6 +1656,10 @@ def build_final_report(checkout_proof, inventory, validation, contamination,
         "queue_status_violations": list(
             queue_status_report.get("violations") or []
         ),
+        "already_landed_handoff_proven": bool(already_landed_handoff.get("proven")),
+        "already_landed_handoff_violations": list(
+            already_landed_handoff.get("reasons") or []
+        ),
         "baseline_validation_proven": bool(baseline_validation.get("proven")),
         "baseline_validation_violations": list(
             baseline_validation.get("violations") or []
@@ -4064,3 +4078,10 @@ def assess_non_mergeable_skip_proof(report_text, **kwargs):
     from reviewer_mergeability_skip import assess_non_mergeable_skip_proof as _assess
 
     return _assess(report_text, **kwargs)
+
+
+def assess_already_landed_handoff_report(report_text, **kwargs):
+    """#299: reject stale fields after the already-landed gate fires."""
+    from reviewer_already_landed_handoff import assess_already_landed_handoff_report as _assess
+
+    return _assess(report_text, **kwargs)