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/useCloned.md

@@ -0,0 +1,91 @@
+---
+category: Utilities
+---
+
+# useCloned
+
+Reactive clone of a ref. By default, it use `JSON.parse(JSON.stringify())` to do the clone.
+
+## Usage
+
+```ts
+import { useCloned } from '@vueuse/core'
+
+const original = ref({ key: 'value' })
+
+const { cloned } = useCloned(original)
+
+original.value.key = 'some new value'
+
+console.log(cloned.value.key) // 'value'
+```
+
+## Manual cloning
+
+```ts
+import { useCloned } from '@vueuse/core'
+
+const original = ref({ key: 'value' })
+
+const { cloned, sync } = useCloned(original, { manual: true })
+
+original.value.key = 'manual'
+
+console.log(cloned.value.key) // 'value'
+
+sync()
+
+console.log(cloned.value.key)// 'manual'
+```
+
+## Custom Clone Function
+
+Using [`klona`](https://www.npmjs.com/package/klona) for example:
+
+```ts
+import { useCloned } from '@vueuse/core'
+import { klona } from 'klona'
+
+const original = ref({ key: 'value' })
+
+const { cloned, isModified, sync } = useCloned(original, { clone: klona })
+```
+
+## Type Declarations
+
+```ts
+export interface UseClonedOptions<T = any> extends WatchOptions {
+  /**
+   * Custom clone function.
+   *
+   * By default, it use `JSON.parse(JSON.stringify(value))` to clone.
+   */
+  clone?: (source: T) => T
+  /**
+   * Manually sync the ref
+   *
+   * @default false
+   */
+  manual?: boolean
+}
+export interface UseClonedReturn<T> {
+  /**
+   * Cloned ref
+   */
+  cloned: Ref<T>
+  /**
+   * Ref indicates whether the cloned data is modified
+   */
+  isModified: Ref<boolean>
+  /**
+   * Sync cloned data with source manually
+   */
+  sync: () => void
+}
+export type CloneFn<F, T = F> = (x: F) => T
+export declare function cloneFnJSON<T>(source: T): T
+export declare function useCloned<T>(
+  source: MaybeRefOrGetter<T>,
+  options?: UseClonedOptions,
+): UseClonedReturn<T>
+```