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/useTextareaAutosize.md

@@ -0,0 +1,94 @@
+---
+category: Browser
+---
+
+# useTextareaAutosize
+
+Automatically update the height of a textarea depending on the content.
+
+## Usage
+
+### Simple example
+
+```vue
+<script setup lang="ts">
+import { useTextareaAutosize } from '@vueuse/core'
+
+const { textarea, input } = useTextareaAutosize()
+</script>
+
+<template>
+  <textarea
+    ref="textarea"
+    v-model="input"
+    class="resize-none"
+    placeholder="What's on your mind?"
+  />
+</template>
+```
+
+::: info
+
+It's recommended to reset the scrollbar styles for the textarea element to avoid incorrect height values for large amounts of text.
+
+```css
+textarea {
+  -ms-overflow-style: none;
+  scrollbar-width: none;
+}
+
+textarea::-webkit-scrollbar {
+  display: none;
+}
+```
+
+:::
+
+### With `rows` attribute
+
+If you need support for the rows attribute on a textarea element, then you should set the `styleProp` option to `minHeight`.
+
+```vue
+<script setup lang="ts">
+import { useTextareaAutosize } from '@vueuse/core'
+
+const { textarea, input } = useTextareaAutosize({ styleProp: 'minHeight' })
+</script>
+
+<template>
+  <textarea
+    ref="textarea"
+    v-model="input"
+    class="resize-none"
+    placeholder="What's on your mind?"
+    rows="3"
+  />
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface UseTextareaAutosizeOptions extends ConfigurableWindow {
+  /** Textarea element to autosize. */
+  element?: MaybeRef<HTMLTextAreaElement | undefined | null>
+  /** Textarea content. */
+  input?: MaybeRef<string>
+  /** Watch sources that should trigger a textarea resize. */
+  watch?: WatchSource | MultiWatchSources
+  /** Function called when the textarea size changes. */
+  onResize?: () => void
+  /** Specify style target to apply the height based on textarea content. If not provided it will use textarea it self.  */
+  styleTarget?: MaybeRef<HTMLElement | undefined>
+  /** Specify the style property that will be used to manipulate height. Can be `height | minHeight`. Default value is `height`. */
+  styleProp?: "height" | "minHeight"
+}
+export interface UseTextareaAutosizeReturn {
+  textarea: Ref<HTMLTextAreaElement | undefined | null>
+  input: Ref<string>
+  triggerResize: () => void
+}
+export declare function useTextareaAutosize(
+  options?: UseTextareaAutosizeOptions,
+): UseTextareaAutosizeReturn
+```