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/useObjectUrl.md

@@ -0,0 +1,55 @@
+---
+category: Browser
+---
+
+# useObjectUrl
+
+Reactive URL representing an object.
+
+Creates an URL for the provided `File`, `Blob`, or `MediaSource` via [URL.createObjectURL()](https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL) and automatically releases the URL via [URL.revokeObjectURL()](https://developer.mozilla.org/en-US/docs/Web/API/URL/revokeObjectURL) when the source changes or the component is unmounted.
+
+## Usage
+
+```vue
+<script setup lang="ts">
+import { useObjectUrl } from '@vueuse/core'
+import { shallowRef } from 'vue'
+
+const file = shallowRef()
+const url = useObjectUrl(file)
+
+function onFileChange(event) {
+  file.value = event.target.files[0]
+}
+</script>
+
+<template>
+  <input type="file" @change="onFileChange">
+
+  <a :href="url">Open file</a>
+</template>
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseObjectUrl v-slot="url" :object="file">
+    <a :href="url">Open file</a>
+  </UseObjectUrl>
+</template>
+```
+
+## Type Declarations
+
+```ts
+/**
+ * Reactive URL representing an object.
+ *
+ * @see https://vueuse.org/useObjectUrl
+ * @param object
+ */
+export declare function useObjectUrl(
+  object: MaybeRefOrGetter<Blob | MediaSource | null | undefined>,
+): Readonly<Ref<string | undefined, string | undefined>>
+```