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/reactivePick.md

@@ -0,0 +1,106 @@
+---
+category: Reactivity
+---
+
+# reactivePick
+
+Reactively pick fields from a reactive object.
+
+## Usage
+
+### Basic Usage
+
+```ts
+import { reactivePick } from '@vueuse/core'
+
+const obj = reactive({
+  x: 0,
+  y: 0,
+  elementX: 0,
+  elementY: 0,
+})
+
+const picked = reactivePick(obj, 'x', 'elementX') // { x: number, elementX: number }
+```
+
+### Predicate Usage
+
+```ts
+import { reactivePick } from '@vueuse/core'
+
+const source = reactive({
+  foo: 'foo',
+  bar: 'bar',
+  baz: 'baz',
+  qux: true,
+})
+const state = reactivePick(source, (value, key) => key !== 'bar' && value !== true)
+// { foo: string, baz: string }
+source.qux = false
+// { foo: string, baz: string, qux: boolean }
+```
+
+### Scenarios
+
+#### Selectively passing props to child
+
+```vue
+<script setup lang="ts">
+import { reactivePick } from '@vueuse/core'
+
+const props = defineProps<{
+  value: string
+  color?: string
+  font?: string
+}>()
+
+const childProps = reactivePick(props, 'color', 'font')
+</script>
+
+<template>
+  <div>
+    <!-- only passes "color" and "font" props to child -->
+    <ChildComp v-bind="childProps" />
+  </div>
+</template>
+```
+
+#### Selectively wrap reactive object
+
+Instead of doing this
+
+```ts
+import { useElementBounding } from '@vueuse/core'
+import { reactive } from 'vue'
+
+const { height, width } = useElementBounding() // object of refs
+const size = reactive({ height, width })
+```
+
+Now we can just have this
+
+```ts
+import { reactivePick, useElementBounding } from '@vueuse/core'
+
+const size = reactivePick(useElementBounding(), 'height', 'width')
+```
+
+## Type Declarations
+
+```ts
+export type ReactivePickReturn<T extends object, K extends keyof T> = {
+  [S in K]: UnwrapRef<T[S]>
+}
+export type ReactivePickPredicate<T> = (
+  value: T[keyof T],
+  key: keyof T,
+) => boolean
+export declare function reactivePick<T extends object, K extends keyof T>(
+  obj: T,
+  ...keys: (K | K[])[]
+): ReactivePickReturn<T, K>
+export declare function reactivePick<T extends object>(
+  obj: T,
+  predicate: ReactivePickPredicate<T>,
+): ReactivePickReturn<T, keyof T>
+```