Schnakenberg — dx/dt=a−x+x²y, dy/dt=b−x²y, dz/dt=c(x−z). Classic a=0.05 b=0.5 c=0.2. Dual a+b sliders. Display embed (x,y,z). Distinct from brusselator.html, oregonator.html, selkov.html, hinshelwood.html, operon.html. Bulk centroid ≈ (0.5412, 3.5142, 0.5474). RK4 chemical fold. Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.