We Put the Proof on a Real FPGA

One verified math source compiles to software, RTL, and a GPU shader. We stopped trusting the model and ran each artifact for real — C on gcc, RTL in Verilator, a shader on an NVIDIA GPU, and the datapath on an Arty A7 FPGA — checking every output against a Lean-proved error bound. Each one held. Building it found six real bugs. Here is the receipt, and here is exactly where it doesn't hold.