New pages don't always appear in sidebar unless you `make clean-doc` and completely rebuild.

When adding a new page in a `toctree`, sometimes it disappears when navigating around the built doc page.

This is only resolved by running `make clean-doc` and rebuilding after that (e.g., `make run`).

I presume this is because all pages need to generate their own sidebar ToC, and when adding a page, only a few pages are rebuilt, so others are not made aware of the new page. That would explain why it doesn't show up all the time.

Is there any easy way to fix this, or at least print a warning that a new page requires a complete rebuild?