type StageKind
How a stage combines into the running elevation.
share: a landform band, scaled by its share of the budget and summed.
carve: subtracts from what the landform bands made — the valleys.
limited: a lattice sum folded through its soft ceiling and added.
remap: rewrites the elevation around a level — the coast.
additive: added as is — the grit.
clamp: the sea's max, on the drawn field alone.
Type
'share' | 'carve' | 'limited' | 'remap' | 'additive' | 'clamp'