docs: record Human Gates identity invariants

tests/test_human_gates_readme.py

@@ -11,6 +11,8 @@ def test_readme_documents_hash_bound_producer_intake_and_revision_decisions():
     assert '"candidate_hash"' in text
     assert "expected_revision" in text
     assert "STACKCHAIN_HUMAN_GATE_DB" in text
+    assert "principal ID and login" in text
+    assert "reopens the exact hash" in text
 
 
 def test_readme_defines_privacy_safe_telegram_coalescing_contract():