docs: add advanced skills for Vitest, Pinia, and Vue built-ins

Add comprehensive reference documentation for:
- Vitest: environments, projects/workspaces, type testing, vi utilities
- Pinia: HMR, Nuxt integration, SSR setup
- Vue: built-in components (Transition, Teleport, Suspense, KeepAlive) and advanced directives

.agents/skills/vueuse-functions/references/useWindowSize.md

@@ -0,0 +1,78 @@
+---
+category: Elements
+---
+
+# useWindowSize
+
+Reactive window size
+
+## Usage
+
+```vue
+<script setup lang="ts">
+import { useWindowSize } from '@vueuse/core'
+
+const { width, height } = useWindowSize()
+</script>
+
+<template>
+  <div>
+    Width: {{ width }}
+    Height: {{ height }}
+  </div>
+</template>
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseWindowSize v-slot="{ width, height }">
+    Width: {{ width }}
+    Height: {{ height }}
+  </UseWindowSize>
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface UseWindowSizeOptions extends ConfigurableWindow {
+  initialWidth?: number
+  initialHeight?: number
+  /**
+   * Listen to window `orientationchange` event
+   *
+   * @default true
+   */
+  listenOrientation?: boolean
+  /**
+   * Whether the scrollbar should be included in the width and height
+   * Only effective when `type` is `'inner'`
+   *
+   * @default true
+   */
+  includeScrollbar?: boolean
+  /**
+   * Use `window.innerWidth` or `window.outerWidth` or `window.visualViewport`
+   * visualViewport documentation from MDN(https://developer.mozilla.org/zh-CN/docs/Web/API/VisualViewport)
+   * @default 'inner'
+   */
+  type?: "inner" | "outer" | "visual"
+}
+export interface UseWindowSizeReturn {
+  width: ShallowRef<number>
+  height: ShallowRef<number>
+}
+/**
+ * Reactive window size.
+ *
+ * @see https://vueuse.org/useWindowSize
+ * @param options
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function useWindowSize(
+  options?: UseWindowSizeOptions,
+): UseWindowSizeReturn
+```