The notes pages were typeset in the default Latin Modern while the slides
used OpenSans and RobotoMono, so the two halves of a presenter page did not
match.
Move the font declarations to fonts.tex, which the slides \input and
mknotes passes to the notes document. mknotes uses it by default when it
exists, so a deck that copies the two notes files in gets matching fonts
without having to remember a flag; --preamble names a different fragment,
and a file named there but missing is an error rather than ignored.
The notes document now compiles from the document directory with
-output-directory rather than running inside the temporary one, so the
relative font paths in the fragment resolve.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
