v1.3.0 — prod12 first promotion (human-opening gate)

New champion from the prod12 training run — the first net trained with the human-opening gate (promotion requires holding a floor on a human-games opening book in addition to the standard arena bar).

Versus the external Ka benchmark (3000 nodes, exhaustive top-20 human openings, 512 sims): 72.5% raw, 96.4% count-weighted, 0.830 sqrt-weighted — the weighted scores are the strongest we have ever measured. Head-to-head it was promoted over the v1.2.0 champion in the internal arena and now serves on the public webapp.

champion.pt attached (TorchScript, 20 input planes, auto-detected by webserve).