A package function that destructures its options object, such as
makeClass({ Base, name }), now specializes per call site like positional
parameters: each destructured name binds the static type of the matching
property, so a class passed as { Base } keeps its static type and
class extends Base builds a constructible subclass.
Fixes#938
Co-authored-by: phall <25888173+phall1@users.noreply.github.com>
