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/watchDeep.md

@@ -0,0 +1,54 @@
+---
+category: Watch
+---
+
+# watchDeep
+
+Shorthand for watching value with `{deep: true}`
+
+## Usage
+
+Similar to `watch`, but with `{ deep: true }`
+
+```ts
+import { watchDeep } from '@vueuse/core'
+
+const nestedObject = ref({ foo: { bar: { deep: 5 } } })
+
+watchDeep(nestedObject, (updated) => {
+  console.log(updated)
+})
+
+onMounted(() => {
+  nestedObject.value.foo.bar.deep = 10
+})
+```
+
+## Type Declarations
+
+```ts
+export declare function watchDeep<
+  T extends Readonly<MultiWatchSources>,
+  Immediate extends Readonly<boolean> = false,
+>(
+  source: [...T],
+  cb: WatchCallback<MapSources<T>, MapOldSources<T, Immediate>>,
+  options?: Omit<WatchOptions<Immediate>, "deep">,
+): WatchHandle
+export declare function watchDeep<
+  T,
+  Immediate extends Readonly<boolean> = false,
+>(
+  source: WatchSource<T>,
+  cb: WatchCallback<T, Immediate extends true ? T | undefined : T>,
+  options?: Omit<WatchOptions<Immediate>, "deep">,
+): WatchHandle
+export declare function watchDeep<
+  T extends object,
+  Immediate extends Readonly<boolean> = false,
+>(
+  source: T,
+  cb: WatchCallback<T, Immediate extends true ? T | undefined : T>,
+  options?: Omit<WatchOptions<Immediate>, "deep">,
+): WatchHandle
+```