Figure out how to test that our system _can't_ do what it _shouldn't_.

[ShapeOfMatter]

e.g. un-projectable choreographies shouldn't type-check; but since they don't typecheck it's hard to write unit tests for that.
e.g. in some of our examples it's significant who doesn't get what; can we express that as a unit test?

[ShapeOfMatter]

I've refactored the core monad to allow the stuff I think we want to allow. I'm not going to merge it until I"m a little more sure it's safe, but i'm realizing it's delicate; our system isn't going to be as "obviously safe" as HasChor's was.

[ShapeOfMatter]

I've refactored the core monad to allow the stuff I think we want to allow. I'm not going to merge it until I"m a little more sure it's safe, but i'm realizing it's delicate; our system isn't going to be as "obviously safe" as HasChor's was.

I've since merged this. See 3507309 and 022d346