max / quasi

Hold the row's fallback in its type, not in a runtime check Slot::beside panicked when the slot had no run, which made a rule the vocabulary depends on enforceable only after the description was already written. Measured across the three shape trees: 58 .beside( sites, 33 with .across( in the same function body and 25 without, so a static same-body check could never have covered it either. Slot::across now takes the row itself. Run::new(fallback) is a Run's only constructor, so a row that has not said what it does when it is tight is unconstructable rather than merely rejected. A bare Fallback still converts, which is what the five MNW tab strips want: a TabGroup fills its own row from its children's labels, so declaring the fallback and no members is the whole statement. Breaking, so the suite goes to 0.100.0 and every consumer requirement moves with it in the same pass.