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/useLastChanged.md

@@ -0,0 +1,63 @@
+---
+category: State
+---
+
+# useLastChanged
+
+Records the timestamp of the last change
+
+## Usage
+
+```ts
+import { useLastChanged } from '@vueuse/core'
+import { nextTick } from 'vue'
+
+const a = ref(0)
+const lastChanged = useLastChanged(a)
+
+a.value = 1
+
+await nextTick()
+
+console.log(lastChanged.value) // 1704709379457
+```
+
+By default the change is recorded on the next tick (`watch()` with `flush: 'post'`). If you want to record the change immediately, pass `flush: 'sync'` as the second argument.
+
+```ts
+import { useLastChanged } from '@vueuse/core'
+
+const a = ref(0)
+const lastChanged = useLastChanged(a, { flush: 'sync' })
+
+a.value = 1
+
+console.log(lastChanged.value) // 1704709379457
+```
+
+## Type Declarations
+
+```ts
+export interface UseLastChangedOptions<
+  Immediate extends boolean,
+  InitialValue extends number | null | undefined = undefined,
+> extends WatchOptions<Immediate> {
+  initialValue?: InitialValue
+}
+export type UseLastChangedReturn =
+  | Readonly<ShallowRef<number | null>>
+  | Readonly<ShallowRef<number>>
+/**
+ * Records the timestamp of the last change
+ *
+ * @see https://vueuse.org/useLastChanged
+ */
+export declare function useLastChanged(
+  source: WatchSource,
+  options?: UseLastChangedOptions<false>,
+): Readonly<ShallowRef<number | null>>
+export declare function useLastChanged(
+  source: WatchSource,
+  options: UseLastChangedOptions<true> | UseLastChangedOptions<boolean, number>,
+): Readonly<ShallowRef<number>>
+```