Grams are the quantity of record

A Measure is only how a quantity is spoken. A component may carry a unit a person would say out loud (two eggs, a glass of juice), but grams is what macros scale from and what a day's total is built on.

lib/measure.ts holds the one invariant, grams === gramsFor(measure), and lib/scan-mapping.ts DROPS a measure that breaks it rather than repairing one. Two quantities that can disagree is the stored-total bug one level down.

Three units: g, ml, piece

cup, tbsp and tsp were removed. They bought a six-tab control and a conversion table for a sentence nobody says about a plate of food.

The server's normaliseMeasure drops an unrecognised unit and keeps the grams before validation, so a stray unit costs a stepper rather than the whole scan.