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/from.md

@@ -0,0 +1,80 @@
+---
+category: '@RxJS'
+---
+
+# from / fromEvent
+
+Wrappers around RxJS's [`from()`](https://rxjs.dev/api/index/function/from) and [`fromEvent()`](https://rxjs.dev/api/index/function/fromEvent) to allow them to accept `ref`s.
+
+## Usage
+
+<!-- TODO: import rxjs error if enable twoslash -->
+
+```ts no-twoslash
+import { from, fromEvent, toObserver, useSubscription } from '@vueuse/rxjs'
+import { interval } from 'rxjs'
+import { map, mapTo, takeUntil, withLatestFrom } from 'rxjs/operators'
+import { shallowRef, useTemplateRef } from 'vue'
+
+const count = shallowRef(0)
+const button = useTemplateRef('buttonRef')
+
+useSubscription(
+  interval(1000)
+    .pipe(
+      mapTo(1),
+      takeUntil(fromEvent(button, 'click')),
+      withLatestFrom(from(count, {
+        immediate: true,
+        deep: false,
+      })),
+      map(([curr, total]) => curr + total),
+    )
+    .subscribe(toObserver(count)), // same as ).subscribe(val => (count.value = val))
+)
+```
+
+## from
+
+The `from` function can accept either a standard RxJS `ObservableInput` or a Vue `ref`. When passed a ref, it creates an Observable that emits whenever the ref's value changes.
+
+### Watch Options
+
+When using `from` with a ref, you can pass Vue's `WatchOptions`:
+
+| Option      | Type                        | Description                        |
+| ----------- | --------------------------- | ---------------------------------- |
+| `immediate` | `boolean`                   | Emit the current value immediately |
+| `deep`      | `boolean`                   | Deeply watch nested objects        |
+| `flush`     | `'pre' \| 'post' \| 'sync'` | Timing of the callback flush       |
+
+## fromEvent
+
+The `fromEvent` function extends RxJS's `fromEvent` to accept a ref to an element. When the ref's value changes (e.g., after the component mounts), it automatically subscribes to the new element.
+
+```ts no-twoslash
+import { fromEvent, useSubscription } from '@vueuse/rxjs'
+import { useTemplateRef } from 'vue'
+
+const button = useTemplateRef('buttonRef')
+
+// Will automatically subscribe when the button element becomes available
+useSubscription(
+  fromEvent(button, 'click').subscribe(() => {
+    console.log('clicked!')
+  })
+)
+```
+
+## Type Declarations
+
+```ts
+export declare function from<T>(
+  value: ObservableInput<T> | Ref<T>,
+  watchOptions?: WatchOptions,
+): Observable<T>
+export declare function fromEvent<T extends HTMLElement | null>(
+  value: MaybeRef<T>,
+  event: string,
+): Observable<Event>
+```