Resolves a union range to its concrete value-shape variants.
Flattens a union range to its value-shape variants in declaration order; takes any other
range to the singleton [shape]. Every returned variant is a concrete value shape, never a nested union, so callers
route each branch without flattening again.
Resolves a union range to its concrete value-shape variants.
Flattens a union range to its value-shape variants in declaration order; takes any other range to the singleton
[shape]. Every returned variant is a concrete value shape, never a nested union, so callers route each branch without flattening again.