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/useElementVisibility.md

@@ -0,0 +1,126 @@
+---
+category: Elements
+---
+
+# useElementVisibility
+
+Tracks the visibility of an element within the viewport.
+
+## Usage
+
+```vue
+<script setup lang="ts">
+import { useElementVisibility } from '@vueuse/core'
+import { useTemplateRef } from 'vue'
+
+const target = useTemplateRef('target')
+const targetIsVisible = useElementVisibility(target)
+</script>
+
+<template>
+  <div ref="target">
+    <h1>Hello world</h1>
+  </div>
+</template>
+```
+
+### rootMargin
+
+If you wish to trigger your callback sooner before the element is fully visible, you can use
+the `rootMargin` option (See [MDN IntersectionObserver/rootMargin](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/rootMargin)).
+
+```ts
+import { useElementVisibility } from '@vueuse/core'
+// ---cut---
+const targetIsVisible = useElementVisibility(target, {
+  rootMargin: '0px 0px 100px 0px',
+})
+```
+
+### threshold
+
+If you want to control the percentage of the visibility required to update the value, you can use the `threshold` option (See [MDN IntersectionObserver/threshold](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver#threshold)).
+
+```ts
+const targetIsVisible = useElementVisibility(target, {
+  threshold: 1.0, // 100% visible
+})
+```
+
+## Component Usage
+
+```vue
+<template>
+  <UseElementVisibility v-slot="{ isVisible }">
+    Is Visible: {{ isVisible }}
+  </UseElementVisibility>
+</template>
+```
+
+## Directive Usage
+
+```vue
+<script setup lang="ts">
+import { vElementVisibility } from '@vueuse/components'
+import { shallowRef, useTemplateRef } from 'vue'
+
+const target = useTemplateRef('target')
+const isVisible = shallowRef(false)
+
+function onElementVisibility(state) {
+  isVisible.value = state
+}
+</script>
+
+<template>
+  <div v-element-visibility="onElementVisibility">
+    {{ isVisible ? 'inside' : 'outside' }}
+  </div>
+
+  <!-- with options -->
+  <div ref="target">
+    <div v-element-visibility="[onElementVisibility, { scrollTarget: target }]">
+      {{ isVisible ? 'inside' : 'outside' }}
+    </div>
+  </div>
+</template>
+```
+
+## Type Declarations
+
+```ts
+export interface UseElementVisibilityOptions
+  extends ConfigurableWindow,
+    Pick<UseIntersectionObserverOptions, "threshold"> {
+  /**
+   * Initial value.
+   *
+   * @default false
+   */
+  initialValue?: boolean
+  /**
+   * @see https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/rootMargin
+   */
+  rootMargin?: MaybeRefOrGetter<string>
+  /**
+   * The element that is used as the viewport for checking visibility of the target.
+   */
+  scrollTarget?: MaybeRefOrGetter<HTMLElement | undefined | null>
+  /**
+   * Stop tracking when element visibility changes for the first time
+   *
+   * @default false
+   */
+  once?: boolean
+}
+/**
+ * Tracks the visibility of an element within the viewport.
+ *
+ * @see https://vueuse.org/useElementVisibility
+ */
+export declare function useElementVisibility(
+  element: MaybeComputedElementRef,
+  options?: UseElementVisibilityOptions,
+): ShallowRef<boolean, boolean>
+export type UseElementVisibilityReturn = ReturnType<typeof useElementVisibility>
+```