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/useArrayDifference.md

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+---
+category: Array
+---
+
+# useArrayDifference
+
+Reactive get array difference of two arrays.
+
+By default, it returns the difference of the first array from the second array, so call `A \ B`, [Relative Complement](<https://en.wikipedia.org/wiki/Complement_(set_theory)>) of B in A.
+
+You can pass the `symmetric` option to get the [Symmetric difference](https://en.wikipedia.org/wiki/Symmetric_difference) of two arrays `A △ B`.
+
+## Usage
+
+### Use with reactive array
+
+```ts
+import { useArrayDifference } from '@vueuse/core'
+
+const list1 = ref([0, 1, 2, 3, 4, 5])
+const list2 = ref([4, 5, 6])
+const result = useArrayDifference(list1, list2)
+// result.value: [0, 1, 2, 3]
+list2.value = [0, 1, 2]
+// result.value: [3, 4, 5]
+```
+
+### Use with reactive array and use function comparison
+
+```ts
+import { useArrayDifference } from '@vueuse/core'
+
+const list1 = ref([{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }, { id: 5 }])
+const list2 = ref([{ id: 4 }, { id: 5 }, { id: 6 }])
+
+const result = useArrayDifference(list1, list2, (value, othVal) => value.id === othVal.id)
+// result.value: [{ id: 1 }, { id: 2 }, { id: 3 }]
+```
+
+### Symmetric Difference
+
+This composable also supports [Symmetric difference](https://en.wikipedia.org/wiki/Symmetric_difference) by passing the `symmetric` option.
+
+```ts {10}
+import { useArrayDifference } from '@vueuse/core'
+
+const list1 = ref([{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }, { id: 5 }])
+const list2 = ref([{ id: 4 }, { id: 5 }, { id: 6 }])
+
+const result = useArrayDifference(
+  list1,
+  list2,
+  (value, othVal) => value.id === othVal.id,
+  { symmetric: true }
+)
+// result.value: [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 6 }]
+```
+
+## Type Declarations
+
+```ts
+export interface UseArrayDifferenceOptions {
+  /**
+   * Returns asymmetric difference
+   *
+   * @see https://en.wikipedia.org/wiki/Symmetric_difference
+   * @default false
+   */
+  symmetric?: boolean
+}
+export type UseArrayDifferenceReturn<T = any> = ComputedRef<T[]>
+export declare function useArrayDifference<T>(
+  list: MaybeRefOrGetter<T[]>,
+  values: MaybeRefOrGetter<T[]>,
+  key?: keyof T,
+  options?: UseArrayDifferenceOptions,
+): UseArrayDifferenceReturn<T>
+export declare function useArrayDifference<T>(
+  list: MaybeRefOrGetter<T[]>,
+  values: MaybeRefOrGetter<T[]>,
+  compareFn?: (value: T, othVal: T) => boolean,
+  options?: UseArrayDifferenceOptions,
+): UseArrayDifferenceReturn<T>
+```