feat(kevin): reconcile Alpaca bracket auto-closes + order status

Bracket stop-loss/take-profit legs fill at Alpaca without passing through the executor, so those closes (and their P&L) were invisible locally.

- broker: add get_order(nested) + list_orders to BaseBroker/AlpacaBroker (+ SimulatedBroker); BrokerOrder carries child legs

- Trade gains broker_order_id (migration f6a7b8c9d0e1); executor stamps the entry order id

- new api_gateway trade-reconcile loop: books a closing SELL + realized P&L when a bracket leg fills (idempotent on the leg order id), syncs PENDING->terminal status, logs drift; runs alongside portfolio_sync

[ci skip]

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_models.py

@@ -123,6 +123,31 @@ class TestTrade:
         assert t.status == TradeStatus.FILLED
         assert t.pnl == 250.50
 
+    def test_trade_broker_order_id_optional(self) -> None:
+        """broker_order_id links a Trade back to its Alpaca order for
+        reconciliation; it is nullable (entry trades set it, manual rows may
+        not)."""
+        t = Trade(
+            id=uuid.uuid4(),
+            ticker="NVDA",
+            side=TradeSide.BUY,
+            qty=10.0,
+            price=100.0,
+            status=TradeStatus.FILLED,
+            broker_order_id="alpaca-ord-abc",
+        )
+        assert t.broker_order_id == "alpaca-ord-abc"
+
+        t2 = Trade(
+            id=uuid.uuid4(),
+            ticker="NVDA",
+            side=TradeSide.BUY,
+            qty=10.0,
+            price=100.0,
+            status=TradeStatus.FILLED,
+        )
+        assert t2.broker_order_id is None
+
 
 class TestPosition:
     def test_create_position(self) -> None: