{# The main navigation, as its own fragment. It is included by base_full.html and served verbatim by /_construct/menu, because a menu that changes between requests cannot only exist in the full-page layout: the sidebar sits outside #main-content, so no Unpoly navigation ever redraws it. `up-source` is what lets construct-core.js reload just this nav when a response's X-Construct-Menu header disagrees with the shell's stamp. Requires `construct` in context. #}