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/watchArray.md

@@ -0,0 +1,53 @@
+---
+category: Watch
+---
+
+# watchArray
+
+Watch for an array with additions and removals.
+
+## Usage
+
+Similar to `watch`, but provides the added and removed elements to the callback function. Pass `{ deep: true }` if the list is updated in place with `push`, `splice`, etc.
+
+```ts
+import { watchArray } from '@vueuse/core'
+
+const list = ref([1, 2, 3])
+
+watchArray(list, (newList, oldList, added, removed) => {
+  console.log(newList) // [1, 2, 3, 4]
+  console.log(oldList) // [1, 2, 3]
+  console.log(added) // [4]
+  console.log(removed) // []
+})
+
+onMounted(() => {
+  list.value = [...list.value, 4]
+})
+```
+
+## Type Declarations
+
+```ts
+export declare type WatchArrayCallback<V = any, OV = any> = (
+  value: V,
+  oldValue: OV,
+  added: V,
+  removed: OV,
+  onCleanup: (cleanupFn: () => void) => void,
+) => any
+/**
+ * Watch for an array with additions and removals.
+ *
+ * @see https://vueuse.org/watchArray
+ */
+export declare function watchArray<
+  T,
+  Immediate extends Readonly<boolean> = false,
+>(
+  source: WatchSource<T[]> | T[],
+  cb: WatchArrayCallback<T[], Immediate extends true ? T[] | undefined : T[]>,
+  options?: WatchOptions<Immediate>,
+): WatchHandle
+```