Fix unmanaged reconciliation review blockers

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

trex_core/adapters/broker/paper.py

@@ -166,6 +166,9 @@ class PaperBroker:
         return [BalanceItem(symbol=sym, hldg_qty=qty)
                 for sym, qty in balances.items() if qty != 0]
 
+    def exposes_full_balance_snapshot(self) -> bool:
+        return True
+
     # --- REQ-038: programmable current price (safety-sell scenario double) ---
     def set_current_price(self, symbol: str, price: Decimal) -> None:
         """Program the current price returned by get_current_price(symbol)."""