[enumeratio]

Fix #442.

The quotient shortcut in their canonical handlers now applies only to a one-operand call, so Numerator(a/b, x) stays a call instead of becoming a. Numerator(a/b) is unchanged.

[arnog]

Thank you, this is landed on main in f601dee (commit, not merge, so the PR is closed rather than merged). It ships in the next release.

Two additions beyond the PR:

• The rational-literal shortcut of Denominator and NumeratorDenominator (a first operand such as 5 or 3/4 read by asRational) had the same gap: Denominator(5, x) still canonicalized to 1. It now carries the same one-operand guard.
• The built-in evaluate handlers refuse a call with more than one operand, the way every other one-operand operator does: Numerator(a/b, x) and Numerator(c, x) evaluate to Error("unexpected-argument", "x") with the frame (Numerator, 2). The canonical form keeps the operands, as in your PR, so a definition that replaces the evaluate handler sees them. The refusal is one error for the whole call, before any broadcast: Denominator(5, []) is the error, not []. An empty Sequence or a Nothing operand does not count as an operand.

Fixes #442.