Money & Unit Price Engine

The obvious unit price -- (priceCents/100)/quantity -- is a float division, and it fails two ways in production. Round it for display before comparing, and a 300-sheet roll at $1.99 becomes $0.00/sheet, silently making every paper product on the shelf compare as free. Or accumulate enough float drift across a large basket or a 3-decimal currency and a total is quietly wrong. Neither throws. Both look like a perfectly normal price.

WHAT SHIPS: a Money type that refuses to let a number enter a money path at all (bigint minor units, per-currency exponents -- JPY has 0, KWD has 3, not a hardcoded 2); conversion factors parsed once into exact bigint rationals (1 lb = 453.59237 g, 1 US fl oz = 29.5735295625 mL); dimension checking on every conversion, so a 300-count bottle cannot convert to sheets; US versus imperial fluid ounce as an explicit locale rather than a guess; unit price and unit-price comparison that stay exact until you round; and allocateMoney / splitMoney with largest-remainder apportionment so a prorated discount sums back to the original total to the cent.

The extraction mutation-tested the suite and found the leftover-cent placement was not actually pinned; it is now. ESM / TypeScript throughout, one dependency.

VERIFIED: 40 tests, measured by running the suite.

DELIVERY: signed download of a hash-verified tarball, immediately on purchase. Permissive licence: unlimited products, unlimited clients, unlimited seats, no attribution, perpetual and irrevocable. One restriction, do not republish the source as source.