New cXML stream guide

.cursor/rules/docs.mdc

@@ -159,6 +159,15 @@ export const products = [
 - Provide alt text for custom images
 - Ensure proper focus management for interactive elements
 
+## Development and build commands
+
+### Package manager
+**This project uses Yarn, not npm.** Always use `yarn` for all package management commands.
+- Build: `yarn --cwd website build`
+- Develop: `yarn --cwd website start` (for local preview)
+- Install: `yarn install`
+- Do NOT use: `npm install`, `npm run`, `npx` - use `yarn` equivalents instead
+
 ## Quality assurance
 
 ### Content review checklist