Permalink targets obscured by sticky nav header

When we (partially) added back the fixed navigation header we failed to add back the logic that translated scroll positions when visiting a page via a permalink hash. Clicking on a timestamp link in a discussion note illustrates this problem:

We had code to handle this in place before we initially removed the sticky navbar. We should find it in the last stable branch that included it and copy it back into our frontend code.

I believe it involved an onload event handler that checked for a window.location.hash as well as an onhashchange event handler that would adjust the scroll position if a same-page permalink anchor is clicked.