Purify the recursive resolver

The recursive resolver is awkward to test because it mixes network calls with business logic. So I just don't test it right now. I test the things it uses, but not it directly. This is a shame, as the recursive resolver is nontrivial.

Purifying it somehow - either making it return some state object and handling the network calls & iteration from a very small function outside it which can easily be eyeballed, or by passing in some "network handle" which can be mocked (ew) - would let me directly test it.

Start by locating the recursive resolver and reading how it currently combines network calls, business logic, and iteration. Compare the proposed state-object boundary with the injectable network-handle approach, then add direct tests that do not require real network calls. Done means the resolver's nontrivial behavior is directly testable while network handling remains in a small, understandable function.

Written by the indexing model from the issue text.