feat: gate reconciliation audit mode from unauthorized cleanup (Closes #419)

Add audit vs cleanup phase tracking so reconciliation audits stay read-only
unless cleanup is explicitly authorized with delete capability proof, safety
proof, and before/after snapshots. Block gitea_delete_branch and merged-cleanup
execution during audit phase, validate final reports for false no-mutations
claims, and document the boundary in the reconcile-landed-pr workflow.

review_proofs.py

@@ -5112,6 +5112,15 @@ def assess_pr_queue_cleanup_report(report_text: str | None) -> dict:
     return _assess(report_text or "")
 
 
+def assess_audit_reconciliation_report(report_text: str | None) -> dict:
+    """#419: validate audit vs cleanup reconciliation report boundaries."""
+    from audit_reconciliation_mode import (
+        assess_audit_reconciliation_report as _assess,
+    )
+
+    return _assess(report_text or "")
+
+
 _GATE_PASSED_VALUE = re.compile(r"\bpassed\b", re.I)
 
 _NOT_APPLICABLE_VALUE = re.compile(