{# The sidebar, written once (backlog #21). Repeating the whole list of entities in every page made the output grow with the square of their number; instead the list is in sidebar.js, written once next to the pages and loaded with a plain script tag (not fetch(), which fails when the docs are opened from disk), and the entries are built in the browser, under the section headers below. Without JavaScript, the headers still link to the trees. #}