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/pinia/references/advanced-hmr.md

@@ -0,0 +1,61 @@
+---
+name: hot-module-replacement
+description: Enable HMR to preserve store state during development
+---
+
+# Hot Module Replacement (HMR)
+
+Pinia supports HMR to edit stores without page reload, preserving existing state.
+
+## Setup
+
+Add this snippet after each store definition:
+
+```ts
+import { defineStore, acceptHMRUpdate } from 'pinia'
+
+export const useAuth = defineStore('auth', {
+  // store options...
+})
+
+if (import.meta.hot) {
+  import.meta.hot.accept(acceptHMRUpdate(useAuth, import.meta.hot))
+}
+```
+
+## Setup Store Example
+
+```ts
+import { defineStore, acceptHMRUpdate } from 'pinia'
+
+export const useCounterStore = defineStore('counter', () => {
+  const count = ref(0)
+  const increment = () => count.value++
+  return { count, increment }
+})
+
+if (import.meta.hot) {
+  import.meta.hot.accept(acceptHMRUpdate(useCounterStore, import.meta.hot))
+}
+```
+
+## Bundler Support
+
+- **Vite:** Officially supported via `import.meta.hot`
+- **Webpack:** Uses `import.meta.webpackHot`
+- Any bundler implementing the `import.meta.hot` spec should work
+
+## Nuxt
+
+With `@pinia/nuxt`, `acceptHMRUpdate` is auto-imported but you still need to add the HMR snippet manually.
+
+## Benefits
+
+- Edit store logic without losing state
+- Add/remove state, actions, and getters on the fly
+- Faster development iteration
+
+<!--
+Source references:
+- https://pinia.vuejs.org/cookbook/hot-module-replacement.html
+-->