fix hitting back on nav, use more css over js for active styling (bug 1058996)

The behavior of the nav should remain the same. Except this fixes hitting "back" on desktop (i.e., there was duplicate pushStates, and hitting back didn't update the nav activness). Fixed by:

- remove duplicate navigation triggering
- defining the tab activeness in CSS using body[data-page-type] rather than CSS
It's actually kind of the same (~50-70px more than the last), I guess because "categories" is a bigger word. I eyeballed these numbers before I even started working on Tarako so it was a long time ago.