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/useNow.md

@@ -0,0 +1,83 @@
+---
+category: Animation
+---
+
+# useNow
+
+Reactive current Date instance.
+
+## Usage
+
+```ts
+import { useNow } from '@vueuse/core'
+
+const now = useNow()
+```
+
+```ts
+import { useNow } from '@vueuse/core'
+// ---cut---
+const { now, pause, resume } = useNow({ controls: true })
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseNow v-slot="{ now, pause, resume }">
+    Now: {{ now }}
+    <button @click="pause()">
+      Pause
+    </button>
+    <button @click="resume()">
+      Resume
+    </button>
+  </UseNow>
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface UseNowOptions<
+  Controls extends boolean,
+> extends ConfigurableScheduler {
+  /**
+   * Expose more controls
+   *
+   * @default false
+   */
+  controls?: Controls
+  /**
+   * Start the clock immediately
+   *
+   * @deprecated Please use `scheduler` option instead
+   * @default true
+   */
+  immediate?: boolean
+  /**
+   * Update interval in milliseconds, or use requestAnimationFrame
+   *
+   * @deprecated Please use `scheduler` option instead
+   * @default requestAnimationFrame
+   */
+  interval?: "requestAnimationFrame" | number
+}
+export type UseNowReturn<Controls extends boolean> = Controls extends true
+  ? {
+      now: Ref<Date>
+    } & Pausable
+  : Ref<Date>
+/**
+ * Reactive current Date instance.
+ *
+ * @see https://vueuse.org/useNow
+ * @param options
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function useNow(options?: UseNowOptions<false>): Ref<Date>
+export declare function useNow(options: UseNowOptions<true>): {
+  now: Ref<Date>
+} & Pausable
+```