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/useTimeout.md

@@ -0,0 +1,113 @@
+---
+category: Animation
+---
+
+# useTimeout
+
+Reactive value that becomes `true` after a given time.
+
+## Usage
+
+```ts
+import { useTimeout } from '@vueuse/core'
+
+const ready = useTimeout(1000)
+```
+
+After 1 second, `ready.value` becomes `true`.
+
+### With Controls
+
+```ts
+import { useTimeout } from '@vueuse/core'
+
+const { ready, start, stop, isPending } = useTimeout(1000, { controls: true })
+
+// Check if timeout is pending
+console.log(isPending.value) // true
+
+// Stop the timeout
+stop()
+
+// Start/restart the timeout
+start()
+```
+
+### Options
+
+| Option      | Type         | Default | Description                                      |
+| ----------- | ------------ | ------- | ------------------------------------------------ |
+| `controls`  | `boolean`    | `false` | Expose `start`, `stop`, and `isPending` controls |
+| `immediate` | `boolean`    | `true`  | Start the timeout immediately                    |
+| `callback`  | `() => void` | —       | Called when the timeout completes                |
+
+### Callback on Timeout
+
+```ts
+import { useTimeout } from '@vueuse/core'
+
+useTimeout(1000, {
+  callback: () => {
+    console.log('Timeout completed!')
+  },
+})
+```
+
+### Reactive Interval
+
+The timeout duration can be reactive:
+
+```ts
+import { useTimeout } from '@vueuse/core'
+
+const duration = ref(1000)
+const ready = useTimeout(duration)
+
+// Change the duration (only affects future timeouts when using controls)
+duration.value = 2000
+```
+
+## Type Declarations
+
+```ts
+export interface UseTimeoutOptions<
+  Controls extends boolean,
+> extends UseTimeoutFnOptions {
+  /**
+   * Expose more controls
+   *
+   * @default false
+   */
+  controls?: Controls
+  /**
+   * Callback on timeout
+   */
+  callback?: Fn
+}
+export type UseTimeoutReturn =
+  | ComputedRef<boolean>
+  | ({
+      readonly ready: ComputedRef<boolean>
+    } & Stoppable)
+/**
+ * @deprecated use UseTimeoutReturn instead
+ */
+export type UseTimoutReturn = UseTimeoutReturn
+/**
+ * Update value after a given time with controls.
+ *
+ * @see   {@link https://vueuse.org/useTimeout}
+ * @param interval
+ * @param options
+ */
+export declare function useTimeout(
+  interval?: MaybeRefOrGetter<number>,
+  options?: UseTimeoutOptions<false>,
+): ComputedRef<boolean>
+export declare function useTimeout(
+  interval: MaybeRefOrGetter<number>,
+  options: UseTimeoutOptions<true>,
+): {
+  ready: ComputedRef<boolean>
+} & Stoppable
+```