pub const CELL_DROP_CLASSES: &[&str];Expand description
Every class saying when a cell of a column drops, including the tier that never does.
The class is a shrink factor: a table short of room takes the shortfall from the columns worth least, and nothing counts positions or names a breakpoint.
CELL_WIDTH_CLASSES’ argument, one column property over: cell-keeps is
the tier the narrowing never hides, so the sheet writes no rule for it and
a scraped set cannot see it.