chore: add CLAUDE.md with project context for AI sessions

Author: quantizor

CLAUDE.md

@@ -0,0 +1,25 @@
+# styled-components Documentation Website
+
+## Build & Test
+- `yarn` to install (Yarn PnP, no package-lock.json)
+- `npx next build` to verify — all pages are statically generated
+- `npx jest -c .jest.config.js` to run tests
+- `npx jest -c .jest.config.js --updateSnapshot` after font/style changes
+- Pre-commit hooks run jest on related files + prettier via lint-staged
+
+## Documentation Structure
+- MDX content lives in `sections/{category}/{topic}.mdx`
+- Each docs page is wired in 3 places: the MDX file, `app/docs/{category}/page.tsx` (import + render), and `app/docs.json` (nav sidebar)
+- Live code examples use ```react blocks (not ```tsx). They have `React`, `styled`, `css`, `keyframes`, `ThemeProvider`, and `render()` in scope. Use `React.useRef()` not `useRef()`.
+- The `components` import path alias `@/` maps to project root
+
+## Key Architecture
+- `lib/registry.tsx` — SSR style registry wrapping root layout. Still needed despite v6.3.0+ RSC support because most components are `'use client'`
+- `utils/fonts.ts` — font family constants using CSS variables `--font-body` and `--font-mono` set via next/font in root layout
+- `components/Anchor.tsx` — renders section headings with anchor links, used across all doc pages
+- Releases page (`app/releases/page.tsx`) fetches from GitHub API and renders with `markdown-to-jsx`
+
+## Gotchas
+- Removing the SSR registry causes FOUC — the site has heavy `'use client'` usage
+- `app/docs.json` section titles must exactly match the `##` heading in the MDX file (used for anchor link generation)
+- Snapshot tests include rendered CSS — any font, style constant, or styled-components version change requires snapshot updates