Add-on rows already carried quantity, unit and extended price; only the name
was exposed. The attribute now renders the full line and a new monetary
sensor reports the add-ons subtotal separately from the box.
The fixture totals were copied from a seven-add-on cart while the fixture
itself had one, so they are now self-consistent and a test asserts that
add-ons plus box price equals the portal's subtotal.
flan