fix(NodeSwitcher): use ui-select-menu/item classes for consistent styling

- Use createPortal to render menu in body
- Add ChevronDown icon
- Add position calculation for menu placement
- Fix ref usage with useRef instead of useState

web/src/components/business/NodeSwitcher.tsx

@@ -1,5 +1,6 @@
-import { useCallback, useEffect, useState } from 'react'
-import { MonitorDot } from 'lucide-react'
+import { useCallback, useEffect, useState, useRef } from 'react'
+import { MonitorDot, ChevronDown } from 'lucide-react'
+import { createPortal } from 'react-dom'
 import {
   activeInterconnectNodeId,
   api,
@@ -15,6 +16,8 @@ export function NodeSwitcher() {
   const [selected, setSelected] = useState(activeInterconnectNodeId || 'local')
   const [isMaster, setIsMaster] = useState(false)
   const [open, setOpen] = useState(false)
+  const [menuStyle, setMenuStyle] = useState<React.CSSProperties>({})
+  const buttonRef = useRef<HTMLButtonElement>(null)
 
   const fetchNodes = useCallback(async () => {
     try {
@@ -93,9 +96,52 @@ export function NodeSwitcher() {
 
   const currentLabel = allOptions.find((o) => o.value === selected)?.label || '本机节点'
 
+  const updateMenuPosition = () => {
+    const el = buttonRef.current
+    if (!el) return
+    const rect = el.getBoundingClientRect()
+    const viewportH = window.innerHeight
+    const spaceBelow = viewportH - rect.bottom
+    const openUp = spaceBelow < 220 && rect.top > spaceBelow
+    setMenuStyle({
+      position: 'fixed',
+      left: rect.left,
+      width: Math.max(rect.width, 140),
+      zIndex: 80,
+      ...(openUp
+        ? { bottom: viewportH - rect.top + 6, top: 'auto' }
+        : { top: rect.bottom + 6, bottom: 'auto' }),
+    })
+  }
+
+  useEffect(() => {
+    if (!open) return
+    updateMenuPosition()
+    const onDoc = (e: MouseEvent) => {
+      const t = e.target as Node
+      if (buttonRef.current?.contains(t)) return
+      setOpen(false)
+    }
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') setOpen(false)
+    }
+    const onReposition = () => updateMenuPosition()
+    document.addEventListener('mousedown', onDoc)
+    document.addEventListener('keydown', onKey)
+    window.addEventListener('resize', onReposition)
+    window.addEventListener('scroll', onReposition, true)
+    return () => {
+      document.removeEventListener('mousedown', onDoc)
+      document.removeEventListener('keydown', onKey)
+      window.removeEventListener('resize', onReposition)
+      window.removeEventListener('scroll', onReposition, true)
+    }
+  }, [open])
+
   return (
     <div className="relative">
       <button
+        ref={buttonRef}
         type="button"
         onClick={() => setOpen(!open)}
         className={cn(
@@ -107,30 +153,24 @@ export function NodeSwitcher() {
       >
         <MonitorDot size={12} className="shrink-0" />
         <span className="max-w-[100px] truncate">{currentLabel}</span>
+        <ChevronDown size={12} className="shrink-0 opacity-60" />
       </button>
 
-      {open && (
-        <div className="absolute left-0 top-full z-[80] mt-1 min-w-[140px] rounded-md border border-[var(--border)] bg-[var(--bg-secondary)] py-1 shadow-lg">
+      {open &&
+        createPortal(
+          <div className="ui-select-menu" style={menuStyle}>
             {allOptions.map((opt) => (
               <button
                 key={opt.value}
                 type="button"
                 onClick={() => handleSelect(opt.value)}
-              className={cn(
-                'w-full px-3 py-1.5 text-left text-xs transition-colors',
-                opt.value === selected
-                  ? 'bg-[var(--bg-selected)] text-[var(--text-primary)]'
-                  : 'text-[var(--text-secondary)] hover:bg-[var(--bg-hover)] hover:text-[var(--text-primary)]',
-              )}
+                className={cn('ui-select-item', opt.value === selected && 'is-active')}
               >
-              {opt.label}
+                <span className="min-w-0 flex-1 truncate">{opt.label}</span>
               </button>
             ))}
-        </div>
-      )}
-
-      {open && (
-        <div className="fixed inset-0 z-[70]" onClick={() => setOpen(false)} />
+          </div>,
+          document.body,
         )}
     </div>
   )