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/useDropZone.md

@@ -0,0 +1,83 @@
+---
+category: Elements
+---
+
+# useDropZone
+
+Create a zone where files can be dropped.
+
+::: warning
+
+Due to Safari browser limitations, file type validation is only possible during the drop event, not during drag events. As a result, the `isOverDropZone` value will always be `true` during drag operations in Safari, regardless of file type.
+
+:::
+
+## Usage
+
+```vue
+<script setup lang="ts">
+import { useDropZone } from '@vueuse/core'
+import { useTemplateRef } from 'vue'
+
+const dropZoneRef = useTemplateRef('dropZoneRef')
+
+function onDrop(files: File[] | null) {
+  // called when files are dropped on zone
+}
+
+const { isOverDropZone } = useDropZone(dropZoneRef, {
+  onDrop,
+  // specify the types of data to be received.
+  dataTypes: ['image/jpeg'],
+  // control multi-file drop
+  multiple: true,
+  // whether to prevent default behavior for unhandled events
+  preventDefaultForUnhandled: false,
+})
+</script>
+
+<template>
+  <div ref="dropZoneRef">
+    Drop files here
+  </div>
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface UseDropZoneReturn {
+  files: ShallowRef<File[] | null>
+  isOverDropZone: ShallowRef<boolean>
+}
+export interface UseDropZoneOptions {
+  /**
+   * Allowed data types, if not set, all data types are allowed.
+   * Also can be a function to check the data types.
+   */
+  dataTypes?:
+    | MaybeRef<readonly string[]>
+    | ((types: readonly string[]) => boolean)
+  /**
+   * Similar to dataTypes, but exposes the DataTransferItemList for custom validation.
+   * If provided, this function takes precedence over dataTypes.
+   */
+  checkValidity?: (items: DataTransferItemList) => boolean
+  onDrop?: (files: File[] | null, event: DragEvent) => void
+  onEnter?: (files: File[] | null, event: DragEvent) => void
+  onLeave?: (files: File[] | null, event: DragEvent) => void
+  onOver?: (files: File[] | null, event: DragEvent) => void
+  /**
+   * Allow multiple files to be dropped. Defaults to true.
+   */
+  multiple?: boolean
+  /**
+   * Prevent default behavior for unhandled events. Defaults to false.
+   */
+  preventDefaultForUnhandled?: boolean
+}
+export declare function useDropZone(
+  target: MaybeRefOrGetter<HTMLElement | Document | null | undefined>,
+  options?: UseDropZoneOptions | UseDropZoneOptions["onDrop"],
+): UseDropZoneReturn
+```