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/useToNumber.md

@@ -0,0 +1,54 @@
+---
+category: Utilities
+---
+
+# useToNumber
+
+Reactively convert a string ref to number.
+
+## Usage
+
+```ts
+import { useToNumber } from '@vueuse/core'
+import { shallowRef } from 'vue'
+
+const str = shallowRef('123')
+const number = useToNumber(str)
+
+number.value // 123
+```
+
+## Type Declarations
+
+```ts
+export interface UseToNumberOptions {
+  /**
+   * Method to use to convert the value to a number.
+   *
+   * Or a custom function for the conversion.
+   *
+   * @default 'parseFloat'
+   */
+  method?: "parseFloat" | "parseInt" | ((value: string | number) => number)
+  /**
+   * The base in mathematical numeral systems passed to `parseInt`.
+   * Only works with `method: 'parseInt'`
+   */
+  radix?: number
+  /**
+   * Replace NaN with zero
+   *
+   * @default false
+   */
+  nanToZero?: boolean
+}
+/**
+ * Reactively convert a string ref to number.
+ *
+ * @__NO_SIDE_EFFECTS__
+ */
+export declare function useToNumber(
+  value: MaybeRefOrGetter<number | string>,
+  options?: UseToNumberOptions,
+): ComputedRef<number>
+```