Consider restoring transitions to controls drawer

[jsoules]

The sticking point here is that the main content div doesn't have a similar transition to fill the space, so we get the controls drawer smoothly zipping away, and then the content div clunks in to fill it all at once.

This most likely can't be fixed in pure CSS, because React is rerendering the component rather than updating its width dimension; however, it's possible that a react package or MUI styling feature could fix it.

Cosmetic--low priority (lower than other cosmetic features)