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/useMath.md

@@ -0,0 +1,47 @@
+---
+category: '@Math'
+---
+
+# useMath
+
+Reactive `Math` methods.
+
+## Usage
+
+```ts
+import { useMath } from '@vueuse/math'
+
+const base = ref(2)
+const exponent = ref(3)
+const result = useMath('pow', base, exponent) // Ref<8>
+
+const num = ref(2)
+const root = useMath('sqrt', num) // Ref<1.4142135623730951>
+
+num.value = 4
+console.log(root.value) // 2
+```
+
+## Type Declarations
+
+```ts
+export type UseMathKeys = keyof {
+  [K in keyof Math as Math[K] extends (...args: any) => any
+    ? K
+    : never]: unknown
+}
+export type UseMathReturn<K extends keyof Math> = ReturnType<
+  Reactified<Math[K], true>
+>
+/**
+ * Reactive `Math` methods.
+ *
+ * @see https://vueuse.org/useMath
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function useMath<K extends keyof Math>(
+  key: K,
+  ...args: ArgumentsType<Reactified<Math[K], true>>
+): UseMathReturn<K>
+```