Land of Lisp also has a good discussion of this topic, but refers to it entirely as "lazy lists" and the like. I think it also convinced me that I want laziness to be almost transparent, so you don't need to have different functions to work with lazy data types versus strict ones. Of course, I'm not opposed to some sort of library adding them in a way that's elegant, even if that library isn't included in Arc.
I'll have to read this more this later, but if you aren't using a unit test library yet, I'd like to pimp mine again: https://bitbucket.org/zck/unit-test.arc/ . I'm willing to write some tests, but that will have to wait until next week, as I'm away this weekend.
That reminds me: I never did get around to adding your test harness to anarki like I promised. I'll do that if I get around to adding some lazy tests this weekend. Otherwise feel free to do so when you look at this again.
Now that anarki has its first suite of tests using your harness, I've designated all prior tests as "old tests" to encourage us to move away from our patchwork of prior solutions.