The distribution shipped sks/tns/ and the mdpdf command in the previous
snapshot without either install guide mentioning them, so the only way to
discover the command was to read env/runtime.env. Both source-install
guides now describe it: what it is for (Markdown that is not Klammertext,
rendered through a headless browser), that runtime.env defines it -- so a
shell started before the installation does not have it -- the two things the
distribution does not install (the renderer's virtual environment, created
by "md_to_pdf.py --setup", and a Chromium-based browser), the MDPDF_*
variables that change its defaults, and where the stylesheet is.
(from dev d8ea0e973914)