feat: Complete fleet — 94 skills across 10+ domains

Pulled ALL skills from 15 source repositories:
- anthropics/skills: 16 (docs, design, MCP, testing)
- obra/superpowers: 14 (TDD, debugging, agents, planning)
- coreyhaines31/marketingskills: 25 (marketing, CRO, SEO, growth)
- better-auth/skills: 5 (auth patterns)
- vercel-labs/agent-skills: 5 (React, design, Vercel)
- antfu/skills: 16 (Vue, Vite, Vitest, pnpm, Turborepo)
- Plus 13 individual skills from various repos

Mosaic Stack is not limited to coding — the Orchestrator and
subagents serve coding, business, design, marketing, writing,
logistics, analysis, and more.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/vueuse-functions/references/useElementSize.md

@@ -0,0 +1,78 @@
+---
+category: Elements
+---
+
+# useElementSize
+
+Reactive size of an HTML element. [ResizeObserver MDN](https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver)
+
+## Usage
+
+```vue
+<script setup lang="ts">
+import { useElementSize } from '@vueuse/core'
+import { useTemplateRef } from 'vue'
+
+const el = useTemplateRef('el')
+const { width, height } = useElementSize(el)
+</script>
+
+<template>
+  <div ref="el">
+    Height: {{ height }}
+    Width: {{ width }}
+  </div>
+</template>
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseElementSize v-slot="{ width, height }">
+    Width: {{ width }} Height: {{ height }}
+  </UseElementSize>
+</template>
+```
+
+## Directive Usage
+
+```vue
+<script setup lang="ts">
+import { vElementSize } from '@vueuse/components'
+
+function onResize({ width, height }: { width: number, height: number }) {
+  console.log(width, height)
+}
+</script>
+
+<template>
+  <textarea v-element-size="onResize" />
+  <!-- with options -->
+  <textarea v-element-size="[onResize, { width: 100, height: 100 }, { box: 'content-box' }]" />
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface ElementSize {
+  width: number
+  height: number
+}
+/**
+ * Reactive size of an HTML element.
+ *
+ * @see https://vueuse.org/useElementSize
+ */
+export declare function useElementSize(
+  target: MaybeComputedElementRef,
+  initialSize?: ElementSize,
+  options?: UseResizeObserverOptions,
+): {
+  width: ShallowRef<number, number>
+  height: ShallowRef<number, number>
+  stop: () => void
+}
+export type UseElementSizeReturn = ReturnType<typeof useElementSize>
+```