FAQ
Why <details>/<summary> instead of a JS toggle? It's expand/collapse
for free, with no extra script and working keyboard/screen-reader support.
Does the scroll-spy affect other pages? No — the script only runs if a
#page-toc element exists on the page, and it's only ever included by this
template.
Can I still hand-write the menu? Yes — set extra.docs_nav in a page's
front matter the way the original version of this demo did, and it takes
priority over the automatic tree for that page.