An equation as math
An equation lhs = rhs is printed as the math of the expression ==(lhs, rhs): the
= is the comparison’s sign at the loosest comparison level. So the Phase 2 round trip
(parseLatex_printLatex, parseTypst_printTypst) reads it back, and a side that is
itself a comparison, and or or is parenthesized by the precedence rules where
needed: on the right always, on the left when it is an and or an or (a comparison
on the left, a < b = c, reads back as the same equation because comparisons
associate to the left).