renderModelOutput now takes the turn's sources and reports back which numbers it
linked, so the list has one source of truth for what the answer actually cited.
Maths runs before citations, not after. A link label has to escape its brackets,
and that escaped form is exactly LaTeX's own display delimiter, so converting the
model's maths first is what stops the maths pass from eating a marker and handing
back a bare 1.
adrianbonpin