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.

tests/test_llm_workflow_split.py

@@ -87,6 +87,14 @@ def test_reconcile_landed_workflow_contract():
     assert "PARTIAL_RECONCILE_COMMENT_THEN_STOP" in text
     assert "RECOVERY_HANDOFF_ONLY" in text
     assert "resolve_partial_reconciliation_plan" in text
+    assert "check_audit_mutation_allowed" in text
+    assert "gitea_authorize_reconciliation_cleanup_phase" in text
+
+
+def test_audit_reconciliation_verifier_exported():
+    from review_proofs import assess_audit_reconciliation_report
+
+    assert callable(assess_audit_reconciliation_report)
 
 
 def test_create_issue_workflow_contract():