**There were two document readers, and a site that says content exists once cannot have two.**
`backoffice/viewer.html` was written before the request to put the list on the left and the
document on the right; once that was done in `<pt-doc-browser>`, there were two implementations
of one thing — and two implementations diverge, always. No page linked to the old one, but
deleting an address that once existed breaks whoever kept it: it becomes a **permalink** that
forwards to `docs.html`, carrying the `#fragment` with it, so the requested document still
opens. There is one reader.