Add affine-correctness tests for the transform registry (°C→°F absolute vs a
delta that must stay offset-free, lb/in factors, inverse round-trips), a
resolver test for the inbound unit aliases, a preferred-unit entry-form label
test, and MCP cases for converting a lb hint to canonical kg and refusing an
unknown unit. Add the structural guard that trips if any dashboard or insight
surface reintroduces a hardcoded transformed-type unit or value scale. Ship the
diagnose/convert script pair for legacy non-canonical measurement rows.
