fix: Alpaca integration bugs — field mapping, market hours, stock symbol handling

- Fix critical bug: Alpaca GetBalance returns wrong field names (total_equity
  vs totalEquity) — auto_trader was getting 0 equity, breaking all decisions
- Fix critical bug: Alpaca GetPositions missing positionAmt/unRealizedProfit
  fields — positions invisible to trading AI
- Fix CancelAllOrders: was nuking ALL orders globally, now filters by symbol
- Implement GetClosedPnL: was returning nil, now returns filled sell orders
- Add IsMarketOpen: checks Alpaca clock endpoint for market hours
- Add market hours check in trading loop: skip cycles when US market closed
  (saves LLM tokens and prevents failed orders)
- Fix parseTradeCommand: 'BUY AAPL 10' no longer becomes 'AAPLUSDT'
- Fix toolGetMarketPrice: route stock symbols to Alpaca, crypto to others
- Add exchange field to toolGetPositions output for multi-exchange clarity

trader/auto_trader_loop.go

@@ -6,6 +6,7 @@ import (
 	"nofx/kernel"
 	"nofx/logger"
 	"nofx/store"
+	"nofx/trader/alpaca"
 	"nofx/wallet"
 	"strings"
 	"time"
@@ -33,6 +34,19 @@ func (at *AutoTrader) runCycle() error {
 		at.checkClaw402Balance()
 	}
 
+	// Check market hours for stock exchanges (Alpaca)
+	if at.exchange == "alpaca" {
+		if alpacaTrader, ok := at.trader.(*alpaca.AlpacaTrader); ok {
+			isOpen, status, err := alpacaTrader.IsMarketOpen()
+			if err != nil {
+				logger.Warnf("⚠️ [%s] Failed to check market clock: %v", at.name, err)
+			} else if !isOpen {
+				logger.Infof("🔒 [%s] US stock market %s — skipping trading cycle #%d", at.name, status, at.callCount)
+				return nil
+			}
+		}
+	}
+
 	// Create decision record
 	record := &store.DecisionRecord{
 		ExecutionLog: []string{},