Add CLAUDE.md for Claude Code session context

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

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+# blog-nextjs
+
+Personal blog built with Next.js 16 (App Router), Contentlayer2, and Tailwind CSS.
+
+## Commands
+- `npm run dev` - Start dev server (Turbopack + Contentlayer2)
+- `npm run build` - Full build (sync-assets → contentlayer2 → next build → pagefind)
+- `npm run sync-assets` - Sync content assets to public/
+
+## Architecture
+- `app/` - Next.js App Router pages
+- `content/` - Git submodule with MDX posts and pages
+- `components/` - React components
+- Contentlayer2 processes MDX from `content/` directory
+- Pagefind provides client-side search
+
+## Conventions
+- TypeScript strict mode
+- Tailwind for styling
+- MDX for blog content