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/usePreferredContrast.md

@@ -0,0 +1,42 @@
+---
+category: Browser
+---
+
+# usePreferredContrast
+
+Reactive [prefers-contrast](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-contrast) media query.
+
+## Usage
+
+```ts
+import { usePreferredContrast } from '@vueuse/core'
+
+const preferredContrast = usePreferredContrast()
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UsePreferredContrast v-slot="{ contrast }">
+    Preferred Contrast: {{ contrast }}
+  </UsePreferredContrast>
+</template>
+```
+
+## Type Declarations
+
+```ts
+export type ContrastType = "more" | "less" | "custom" | "no-preference"
+/**
+ * Reactive prefers-contrast media query.
+ *
+ * @see https://vueuse.org/usePreferredContrast
+ * @param [options]
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function usePreferredContrast(
+  options?: ConfigurableWindow,
+): ComputedRef<ContrastType>
+```