Add AGENTS.md with Cursor Cloud specific instructions

Co-authored-by: boojack <stevenlgtm@gmail.com>

Author: cursoragent

AGENTS.md

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+# AGENTS.md
+
+## Cursor Cloud specific instructions
+
+This is a **Next.js 16 static marketing/docs website** for Memos (usememos.com). No external services, databases, or environment variables are required.
+
+### Services
+
+| Service | Command | Port | Notes |
+|---------|---------|------|-------|
+| Dev server | `pnpm dev` | 3000 | Uses Turbopack; hot-reloads on file changes |
+
+### Key commands
+
+Refer to `CLAUDE.md` and `package.json` scripts for the full list. Quick reference:
+
+- **Lint**: `pnpm lint` (runs Biome)
+- **Format**: `pnpm format` (runs Biome format with `--write`)
+- **Build**: `pnpm build` (full production build, generates 300+ static pages)
+- **Dev**: `pnpm dev` (starts on port 3000 with Turbopack)
+
+### Gotchas
+
+- The `postinstall` script downloads OpenAPI specs from GitHub (`raw.githubusercontent.com`) and generates MDX + Fumadocs source files. If the network fetch fails during `pnpm install`, the generated API docs will be missing. Rerun `pnpm install` to retry.
+- pnpm may warn about ignored build scripts for `esbuild` and `sharp`. This warning is cosmetic and does not block development or builds.
+- There are no automated test suites (no `test` script in `package.json`). Verification is done via `pnpm lint` and `pnpm build`.
+- The `.source/` directory is auto-generated by `fumadocs-mdx` during `postinstall`. Do not edit files in it directly.