This is a scalar set in that the keys can only be atomic values, primitives or remotables. Other storeSets will accept, for example, copyArrays and copyRecords, as keys and look them up based on equality of their contents.

TODO For now, this scalarWeakSet accepts only remotables, reflecting the constraints of the underlying JavaScript WeakSet it uses internally. But it should accept the primitives as well, storing them in a separate internal set. What makes it "weak" is that it provides no API for enumerating what's there. Though note that this would only enables collection of the remotables, since the other primitives may always appear.