fix: HL size 动态格式化（从 Meta 取 szDecimals）

- 新增 HyperLiquidTrade.GetSize()，从 HL Meta.Universe 获取
  每个币的 SzDecimals 运行时格式化订单数量
- 替代硬编码的 exchange.GetHLSize() switch case
- trader.go 中 placeOrder/placeOrderAt 两处调用切换为新方法
- 新增 TryEntry 价格<=0 检查，过滤异常数据

trader.go

@@ -488,6 +488,12 @@ func (t *Trader) TryEntry(opp *ArbOpportunity, store *PriceStore, notifier *Noti
 		return false
 	}
 
+	// Data quality: reject if either price is zero or negative (stale/fake data)
+	if opp.BuyPrice <= 0 || opp.SellPrice <= 0 {
+		log.Printf("[Trader] %s: skip entry (price=%v/%v <= 0), likely stale/delisted coin", opp.Coin, opp.BuyPrice, opp.SellPrice)
+		return false
+	}
+
 	t.mu.Lock()
 	if t.shuttingDown {
 		t.mu.Unlock()
@@ -1159,7 +1165,7 @@ func (t *Trader) placeOrder(leg *PositionLeg, side string, store *PriceStore) (s
 		}
 		return "", fee
 	} else {
-		size := exchange.GetHLSize(leg.Coin, t.cfg.TradeAmountUSD, leg.EntryPrice)
+		size := t.hyperliquid.GetSize(leg.Coin, t.cfg.TradeAmountUSD, leg.EntryPrice)
 		resp, err := t.hyperliquid.PlaceMarketOrder(leg.Coin, side, size)
 		if err != nil {
 			return fmt.Sprintf("HL %s error: %v", side, err), 0
@@ -1544,7 +1550,7 @@ func (t *Trader) placeOrderAt(leg *PositionLeg, side string, store *PriceStore,
 			return fmt.Sprintf("BG %s error: %v", side, err)
 		}
 	} else {
-		size := exchange.GetHLSize(leg.Coin, t.cfg.TradeAmountUSD, price)
+		size := t.hyperliquid.GetSize(leg.Coin, t.cfg.TradeAmountUSD, price)
 		_, err := t.hyperliquid.PlaceMarketOrder(leg.Coin, side, size)
 		if err != nil {
 			return fmt.Sprintf("HL %s error: %v", side, err)