docs: add AGENTS.md

Author: chenjiahan

AGENTS.md

@@ -0,0 +1,40 @@
+# AGENTS.md
+
+## Stack
+
+- Use repo Node.js/pnpm versions (`package.json`)
+- `pnpm` workspace; shared deps in `pnpm-workspace.yaml` catalogs
+- TypeScript, Rsbuild/Rslib/Rstest/Rslint, Oxfmt
+
+## Commands
+
+```bash
+# setup
+corepack enable && pnpm install
+
+# dev checks
+pnpm lint
+pnpm test
+
+# build / format / spelling
+pnpm build
+pnpm format
+pnpm check:format
+pnpm check:spell
+
+# focused work
+pnpm --filter rstack build
+pnpm --filter rstack test
+```
+
+## Testing
+
+- Run `pnpm build` once before `pnpm test` command
+
+## Project structure
+
+```text
+packages/rstack/       # CLI package
+examples/*             # example projects
+scripts/               # repo tooling
+```