fix(SubTabContainer): 保持 Tab 面板挂载状态，防止切换时状态丢失

- 添加 lazyBehavior="keepMounted" 属性
- 修复切换一级 Tab 后二级 Tab 状态被完全重置的问题
- 组件仍然懒加载，但首次渲染后保持挂载

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/components/SubTabContainer/index.tsx

@@ -193,6 +193,7 @@ const SubTabContainer: React.FC<SubTabContainerProps> = memo(({
     <Box>
       <Tabs
         isLazy={isLazy}
+        lazyBehavior="keepMounted"
         variant="unstyled"
         index={currentIndex}
         onChange={handleTabChange}