Pure-function coverage of the validator that normalizes dollars→cents and
rejects bad input before it touches a balance: required-field errors +
field tag, dollars→cents conversion, positive-amount enforcement (rejects
0/negative/non-numeric; documents the intentional lack of an upper bound),
real-calendar-date validation (Feb 30 / month 13), payment_source
whitelist, and the require* option matrix. Suite 215 green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>