Two issues making year/sup/source tags at the bottom unusable:
1. col: namespace rendered 138 column-metadata buttons (62% of all
tags) with 65-char labels, pushing useful tags below the fold.
These are internal column documentation, not browsing categories.
Now filtered out of the sidebar tag list.
2. Sidebar had no overflow scroll or sticky positioning. Tags below
the viewport were unreachable. Now sticky with overflow-y: auto.
Sidebar now shows 85 tags (was 223), all reachable via scroll.
refs #71
21a6035bf3
