Problem: ids like documentation, download, support, about
in the top menu collide with the same ids used inside documents.
This breaks HTML validation (duplicate ids) and the associated
<label for=...> behaviour.
Fix: rename them the same way footer.html already does — prefix
with the section name, e.g. header-documentation-title.
Note: id="name" is left as is. This means [[name]] anchors are
implicitly unavailable on the site, since "name" is already taken
by the top menu. If such an anchor is ever needed, either the
header id or the document anchor must be renamed.