chore: Add agentic coding tooling

.crosslink/rules/javascript-react.md

@@ -0,0 +1,44 @@
+### JavaScript/React Best Practices
+
+#### Component Structure
+- Use functional components with hooks
+- Keep components small and focused (< 200 lines)
+- Extract custom hooks for reusable logic
+- Use PropTypes for runtime type checking
+
+```javascript
+// GOOD: Clear component with PropTypes
+import PropTypes from 'prop-types';
+
+const UserCard = ({ user, onSelect }) => {
+    return (
+        <div onClick={() => onSelect(user.id)}>
+            {user.name}
+        </div>
+    );
+};
+
+UserCard.propTypes = {
+    user: PropTypes.shape({
+        id: PropTypes.string.isRequired,
+        name: PropTypes.string.isRequired,
+    }).isRequired,
+    onSelect: PropTypes.func.isRequired,
+};
+```
+
+#### State Management
+- Use `useState` for local state
+- Use `useReducer` for complex state logic
+- Lift state up only when needed
+- Consider context for deeply nested prop drilling
+
+#### Performance
+- Use `React.memo` for expensive pure components
+- Use `useMemo` and `useCallback` appropriately
+- Avoid inline object/function creation in render
+
+#### Security
+- Never use `dangerouslySetInnerHTML` with user input
+- Sanitize URLs before using in `href` or `src`
+- Validate props at component boundaries