worldproof: diagnosing where world-model predictions break and a measurement of when pixel metrics stop being able to rank models at all [P]

I've been building an open-source tool for diagnosing world models, the kind that predict future frames from a starting context and a sequence of actions. It compares a rollout against ground truth and against physical invariants, then tells you where and why the prediction falls apart. It doesn't score task success or planning quality on purpose, since there are already benchmarks for those. While validating it I ran into something I think is more interesting than the tool itself. ## Pixel metrics on real robot video often can't rank models at all I ran a copy the last frame baseline, which i