docs: add advanced skills for Vitest, Pinia, and Vue built-ins

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- Vue: built-in components (Transition, Teleport, Suspense, KeepAlive) and advanced directives

.agents/skills/vueuse-functions/references/useResizeObserver.md

@@ -0,0 +1,108 @@
+---
+category: Elements
+---
+
+# useResizeObserver
+
+Reports changes to the dimensions of an Element's content or the border-box
+
+## Usage
+
+```vue
+<script setup lang="ts">
+import { useResizeObserver } from '@vueuse/core'
+import { ref, useTemplateRef } from 'vue'
+
+const el = useTemplateRef('el')
+const text = ref('')
+
+useResizeObserver(el, (entries) => {
+  const entry = entries[0]
+  const { width, height } = entry.contentRect
+  text.value = `width: ${width}, height: ${height}`
+})
+</script>
+
+<template>
+  <div ref="el">
+    {{ text }}
+  </div>
+</template>
+```
+
+## Directive Usage
+
+```vue
+<script setup lang="ts">
+import { vResizeObserver } from '@vueuse/components'
+
+const text = ref('')
+
+function onResizeObserver(entries) {
+  const [entry] = entries
+  const { width, height } = entry.contentRect
+  text.value = `width: ${width}, height: ${height}`
+}
+</script>
+
+<template>
+  <div v-resize-observer="onResizeObserver">
+    {{ text }}
+  </div>
+</template>
+```
+
+[ResizeObserver MDN](https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver)
+
+## Type Declarations
+
+```ts
+/**
+ * @deprecated This interface is now available in the DOM lib.
+ * Use the global {@link globalThis.ResizeObserverSize} instead.
+ */
+export interface ResizeObserverSize {
+  readonly inlineSize: number
+  readonly blockSize: number
+}
+/**
+ * @deprecated This interface is now available in the DOM lib.
+ * Use the global {@link globalThis.ResizeObserverEntry} instead.
+ */
+export interface ResizeObserverEntry {
+  readonly target: Element
+  readonly contentRect: DOMRectReadOnly
+  readonly borderBoxSize: ReadonlyArray<ResizeObserverSize>
+  readonly contentBoxSize: ReadonlyArray<ResizeObserverSize>
+  readonly devicePixelContentBoxSize: ReadonlyArray<ResizeObserverSize>
+}
+/**
+ * @deprecated This interface is now available in the DOM lib.
+ * Use the global {@link globalThis.ResizeObserverCallback} instead.
+ */
+export type ResizeObserverCallback = (
+  entries: ReadonlyArray<ResizeObserverEntry>,
+  observer: ResizeObserver,
+) => void
+export interface UseResizeObserverOptions
+  extends ResizeObserverOptions, ConfigurableWindow {}
+export interface UseResizeObserverReturn extends Supportable {
+  stop: () => void
+}
+/**
+ * Reports changes to the dimensions of an Element's content or the border-box
+ *
+ * @see https://vueuse.org/useResizeObserver
+ * @param target
+ * @param callback
+ * @param options
+ */
+export declare function useResizeObserver(
+  target:
+    | MaybeComputedElementRef
+    | MaybeComputedElementRef[]
+    | MaybeRefOrGetter<MaybeElement[]>,
+  callback: globalThis.ResizeObserverCallback,
+  options?: UseResizeObserverOptions,
+): UseResizeObserverReturn
+```