Render the infobox on the client side. This removes a lot of cached crap on the server side, and just generally makes so much more sense. It makes fullscreen setup a bit slower (though not that much, thanks to a new covering partial index). Interestingly, it now more often shows the infobox on mobile, since it no longer cares about text overflow; it's possible we should try to do something about that.
Rework preloading. This now puts the preload to the left or to the right of the screen; it tries to simplify things, but unfortunately, kicks into less-than helpful browser behavior with scrolling to show offscreen elements. I've kept it primarily because it will make the upcoming swipe changes easier.