TL;DR

Some things can't be checked with a number, like whether an animation feels right.

So a second, read-only agent grades the first one against a written rubric it is not allowed to edit.

In my run the reviewer rejected the builder three times, and the most interesting problem it caught was in the test evidence, not the code.

In Part 1 I built a loop that chased a number, frames per second. But most of what we care about in software is not a number. "Does this region switch feel good?" has no assert. You cannot write expect(feelsRight).toBe(true).