build(agent): melter#14fd4b iteration

src/idea156_kappabridge_privacy_safe/storage.py

@@ -155,6 +155,16 @@ class FederationStore:
             row = session.execute(select(LedgerRow).order_by(LedgerRow.seq.desc())).scalars().first()
             return 0 if row is None else row.seq
 
+    def ledger_root(self) -> str:
+        """Return the latest ledger entry hash, or a zeroed hash if the ledger is empty.
+
+        This is a convenience accessor used by auditors to quickly obtain the
+        tamper-evident tip of the governance ledger.
+        """
+        with self.session() as session:
+            row = session.execute(select(LedgerRow).order_by(LedgerRow.seq.desc())).scalars().first()
+            return row.entry_hash if row is not None else "0" * 64
+
     @staticmethod
     def _row_to_contract_dict(row: ContractRow) -> dict[str, Any]:
         return {

tests/test_ledger_root.py

@@ -0,0 +1,16 @@
+# simple test to assert ledger_root reflects the latest recorded event
+from __future__ import annotations
+
+from pathlib import Path
+
+from idea156_kappabridge_privacy_safe import FederationStore
+
+
+def test_ledger_root_updates(tmp_path: Path) -> None:
+    store = FederationStore(tmp_path / "ledger.db")
+    # initially empty ledger -> zeroed hash
+    assert store.ledger_root() == "0" * 64
+
+    # record an event and ensure ledger_root updates
+    rec = store.record_event("test_event", {"foo": "bar"})
+    assert store.ledger_root() == rec["entry_hash"]