You can see what's probably the same issue in Firefox/Chromium as well: You can't scroll e.g. https://tract-docs.dev/docs/getting-started/ with the keyboard without first clicking into the page.
For a documentation thing like this, I’d generally recommend avoiding a separate scrolling pane for the primary content, but rather arranging so that it can use the document’s scrolling element. This gets the scrollbar in the place people generally expect it in web things, and makes it work regardless of whether the JS loads.