预热线程增加 I/O 异常保护，避免进程关闭时 file closed 报错

frontend/components/dashboard/ScanTerminalDashboard.tsx

@@ -8,7 +8,6 @@ import {
   ChevronLeft,
   ChevronRight,
   GraduationCap,
-  LineChart,
   Menu,
   Search,
   Table2,
@@ -473,7 +472,6 @@ function PolyWeatherTerminal({
 
   const NAV_ITEMS = [
     { key: "contracts", Icon: Table2, labelEn: "Contracts", labelZh: "天气合约" },
-    { key: "signals", Icon: LineChart, labelEn: "Signals", labelZh: "交易信号" },
     { key: "markets", Icon: Activity, labelEn: "Markets", labelZh: "市场概览" },
     { key: "training", Icon: GraduationCap, labelEn: "Training", labelZh: "训练数据" },
   ];