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/useDevicePixelRatio.md

@@ -0,0 +1,47 @@
+---
+category: Sensors
+---
+
+# useDevicePixelRatio
+
+Reactively track [`window.devicePixelRatio`](https://developer.mozilla.org/docs/Web/API/Window/devicePixelRatio)
+
+> NOTE: there is no event listener for `window.devicePixelRatio` change. So this function uses [`Testing media queries programmatically (window.matchMedia)`](https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Testing_media_queries) applying the same mechanism as described in [this example](https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio#monitoring_screen_resolution_or_zoom_level_changes).
+
+## Usage
+
+```ts
+import { useDevicePixelRatio } from '@vueuse/core'
+
+const { pixelRatio } = useDevicePixelRatio()
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseDevicePixelRatio v-slot="{ pixelRatio }">
+    Pixel Ratio: {{ pixelRatio }}
+  </UseDevicePixelRatio>
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface UseDevicePixelRatioOptions extends ConfigurableWindow {}
+export interface UseDevicePixelRatioReturn {
+  pixelRatio: ShallowRef<number>
+  stop: WatchStopHandle
+}
+/**
+ * Reactively track `window.devicePixelRatio`.
+ *
+ * @see https://vueuse.org/useDevicePixelRatio
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function useDevicePixelRatio(
+  options?: UseDevicePixelRatioOptions,
+): UseDevicePixelRatioReturn
+```