Nicholai 827f13a2db feat(skills): add agent skills for claude code
add web-perf and vercel-react-best-practices skills from skills.sh
to improve ai assistance for this next.js + cloudflare workers project.

- web-perf: core web vitals analysis and performance auditing
- vercel-react-best-practices: react/next.js optimization patterns
- wrangler: cloudflare workers cli guidance (already existed)
2026-01-22 11:40:05 -07:00

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Markdown

---
title: Subscribe to Derived State
impact: MEDIUM
impactDescription: reduces re-render frequency
tags: rerender, derived-state, media-query, optimization
---
## Subscribe to Derived State
Subscribe to derived boolean state instead of continuous values to reduce re-render frequency.
**Incorrect (re-renders on every pixel change):**
```tsx
function Sidebar() {
const width = useWindowWidth() // updates continuously
const isMobile = width < 768
return <nav className={isMobile ? 'mobile' : 'desktop'} />
}
```
**Correct (re-renders only when boolean changes):**
```tsx
function Sidebar() {
const isMobile = useMediaQuery('(max-width: 767px)')
return <nav className={isMobile ? 'mobile' : 'desktop'} />
}
```