Benchmark $/token for a model on vLLM in Chalk

Produces a defensible cost-per-token number: serve the model on a GPU, drive it to saturation, confirm the GPU is actually the limiter, then divide authoritative cloud pricing by measured throughput.

The order matters. A throughput number without a saturation check is unfalsifiable, and a $/hr figure pulled from a blog post is usually wrong (see step 5).

1. Serve the model