fix: 修复 useIsMobile 的抖动问题

现在移动端判定会：

- 忽略 VS Code webview/iframe 隐藏时的尺寸变化
- 忽略 0 宽这类无效 viewport
- 在 matchMedia / resize 后延迟 120ms 再确认真实宽度

这样 tab 切走再回来时，不会因为短暂小宽度进入 mobile 分支，也就不会把日志分析桌面布局卸载再重新加载

Author: Windsland52

src/composables/useIsMobile.ts

@@ -2,12 +2,52 @@ import { ref } from 'vue'
 import type { Ref } from 'vue'
 
 const MOBILE_BREAKPOINT = '(max-width: 768px)'
+const MOBILE_BREAKPOINT_WIDTH = 768
+const LAYOUT_STABILIZE_DELAY_MS = 120
 
 const mediaQuery = window.matchMedia(MOBILE_BREAKPOINT)
-const isMobile = ref(mediaQuery.matches)
 
-mediaQuery.addEventListener('change', (e) => {
-  isMobile.value = e.matches
+const readViewportWidth = (): number | null => {
+  const candidates = [
+    window.visualViewport?.width,
+    window.innerWidth,
+    document.documentElement?.clientWidth,
+  ].filter((value): value is number => typeof value === 'number' && Number.isFinite(value))
+
+  const width = Math.max(0, ...candidates)
+  return width > 0 ? width : null
+}
+
+const readStableMobileState = (): boolean | null => {
+  if (document.visibilityState === 'hidden') return null
+  const width = readViewportWidth()
+  if (width == null) return null
+  return width <= MOBILE_BREAKPOINT_WIDTH
+}
+
+const isMobile = ref(readStableMobileState() ?? mediaQuery.matches)
+let pendingUpdate: ReturnType<typeof setTimeout> | null = null
+
+const commitStableMobileState = () => {
+  pendingUpdate = null
+  const next = readStableMobileState()
+  if (next == null) return
+  isMobile.value = next
+}
+
+const scheduleStableMobileUpdate = () => {
+  if (pendingUpdate) clearTimeout(pendingUpdate)
+  pendingUpdate = setTimeout(commitStableMobileState, LAYOUT_STABILIZE_DELAY_MS)
+}
+
+mediaQuery.addEventListener('change', () => {
+  scheduleStableMobileUpdate()
+})
+
+window.addEventListener('resize', scheduleStableMobileUpdate)
+window.visualViewport?.addEventListener('resize', scheduleStableMobileUpdate)
+document.addEventListener('visibilitychange', () => {
+  if (document.visibilityState === 'visible') scheduleStableMobileUpdate()
 })
 
 export function useIsMobile(): { isMobile: Ref<boolean> } {