How does useOptimistic in React 19 work, how does it automatically roll back on error, and how does it compare to manually managing optimistic state?

Imagine you're playing a game where you can press a button to get a star, but the star takes a little time to appear. useOptimistic is like pretending you already have the star right away, so you feel happy. If the star doesn't come, the game automatically takes away the pretend star, so you know to wait.