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/isDefined.md

@@ -0,0 +1,31 @@
+---
+category: Utilities
+---
+
+# isDefined
+
+Non-nullish checking type guard for Ref.
+
+## Usage
+
+```ts
+import { isDefined } from '@vueuse/core'
+
+const example = ref(Math.random() ? 'example' : undefined) // Ref<string | undefined>
+
+if (isDefined(example))
+  example // Ref<string>
+```
+
+## Type Declarations
+
+```ts
+export type IsDefinedReturn = boolean
+export declare function isDefined<T>(
+  v: ComputedRef<T>,
+): v is ComputedRef<Exclude<T, null | undefined>>
+export declare function isDefined<T>(
+  v: Ref<T>,
+): v is Ref<Exclude<T, null | undefined>>
+export declare function isDefined<T>(v: T): v is Exclude<T, null | undefined>
+```