Compare useTransition and useDeferredValue: when do you own the state update vs receive a value, how do their loading signals differ, and can they be combined?

Imagine you're building with LEGOs. Sometimes you want to start building a new tower right away (useTransition) and show a 'building' sign. Other times you get a new LEGO piece from a friend and you want to finish your current tower first before using it (useDeferredValue). Both help keep your play smooth and not freeze.