operator [] method
Looks up the generated scoped class name for author className.
Returns the scoped class name if defined in the stylesheet (e.g. 'card_title__a1b2c3d').
If className was not present in the scoped stylesheet (such as a global utility
class like 'flex' or 'p-4'), returns className unchanged so utility classes
pass through safely without throwing.
final cls = styles['card']; // Scoped: 'card_card__a1b2c3d'
final util = styles['flex']; // Pass-through: 'flex'
Implementation
String operator [](String className) => classes[className] ?? className;