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/useTimeAgo.md

@@ -0,0 +1,154 @@
+---
+category: Time
+---
+
+# useTimeAgo
+
+Reactive time ago. Automatically update the time ago string when the time changes.
+
+## Usage
+
+```ts
+import { useTimeAgo } from '@vueuse/core'
+
+const timeAgo = useTimeAgo(new Date(2021, 0, 1))
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseTimeAgo v-slot="{ timeAgo }" :time="new Date(2021, 0, 1)">
+    Time Ago: {{ timeAgo }}
+  </UseTimeAgo>
+</template>
+```
+
+## Non-Reactivity Usage
+
+In case you don't need the reactivity, you can use the `formatTimeAgo` function to get the formatted string instead of a Ref.
+
+```ts
+import { formatTimeAgo } from '@vueuse/core'
+
+const timeAgo = formatTimeAgo(new Date(2021, 0, 1)) // string
+```
+
+## Type Declarations
+
+```ts
+export type UseTimeAgoFormatter<T = number> = (
+  value: T,
+  isPast: boolean,
+) => string
+export type UseTimeAgoUnitNamesDefault =
+  | "second"
+  | "minute"
+  | "hour"
+  | "day"
+  | "week"
+  | "month"
+  | "year"
+export interface UseTimeAgoMessagesBuiltIn {
+  justNow: string
+  past: string | UseTimeAgoFormatter<string>
+  future: string | UseTimeAgoFormatter<string>
+  invalid: string
+}
+export type UseTimeAgoMessages<
+  UnitNames extends string = UseTimeAgoUnitNamesDefault,
+> = UseTimeAgoMessagesBuiltIn &
+  Record<UnitNames, string | UseTimeAgoFormatter<number>>
+export interface FormatTimeAgoOptions<
+  UnitNames extends string = UseTimeAgoUnitNamesDefault,
+> {
+  /**
+   * Maximum unit (of diff in milliseconds) to display the full date instead of relative
+   *
+   * @default undefined
+   */
+  max?: UnitNames | number
+  /**
+   * Formatter for full date
+   */
+  fullDateFormatter?: (date: Date) => string
+  /**
+   * Messages for formatting the string
+   */
+  messages?: UseTimeAgoMessages<UnitNames>
+  /**
+   * Minimum display time unit (default is minute)
+   *
+   * @default false
+   */
+  showSecond?: boolean
+  /**
+   * Rounding method to apply.
+   *
+   * @default 'round'
+   */
+  rounding?: "round" | "ceil" | "floor" | number
+  /**
+   * Custom units
+   */
+  units?: UseTimeAgoUnit<UnitNames>[]
+}
+export interface UseTimeAgoOptions<
+  Controls extends boolean,
+  UnitNames extends string = UseTimeAgoUnitNamesDefault,
+>
+  extends FormatTimeAgoOptions<UnitNames>, ConfigurableScheduler {
+  /**
+   * Expose more controls
+   *
+   * @default false
+   */
+  controls?: Controls
+  /**
+   * Intervals to update, set 0 to disable auto update
+   *
+   * @deprecated Please use `scheduler` option instead
+   * @default 30_000
+   */
+  updateInterval?: number
+}
+export interface UseTimeAgoUnit<
+  Unit extends string = UseTimeAgoUnitNamesDefault,
+> {
+  max: number
+  value: number
+  name: Unit
+}
+export type UseTimeAgoReturn<Controls extends boolean = false> =
+  Controls extends true
+    ? {
+        timeAgo: ComputedRef<string>
+      } & Pausable
+    : ComputedRef<string>
+/**
+ * Reactive time ago formatter.
+ *
+ * @see https://vueuse.org/useTimeAgo
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function useTimeAgo<
+  UnitNames extends string = UseTimeAgoUnitNamesDefault,
+>(
+  time: MaybeRefOrGetter<Date | number | string>,
+  options?: UseTimeAgoOptions<false, UnitNames>,
+): UseTimeAgoReturn<false>
+export declare function useTimeAgo<
+  UnitNames extends string = UseTimeAgoUnitNamesDefault,
+>(
+  time: MaybeRefOrGetter<Date | number | string>,
+  options: UseTimeAgoOptions<true, UnitNames>,
+): UseTimeAgoReturn<true>
+export declare function formatTimeAgo<
+  UnitNames extends string = UseTimeAgoUnitNamesDefault,
+>(
+  from: Date,
+  options?: FormatTimeAgoOptions<UnitNames>,
+  now?: Date | number,
+): string
+```