Selkov — dx/dt=−x+a·y+x²y, dy/dt=b−a·y−x²y, dz/dt=μ(x−z). Classic a=0.08 b=0.6 μ=0.1. Dual a+b sliders. Display embed (x,y,z). Distinct from operon.html, brusselator.html, oregonator.html, hinshelwood.html, schnakenberg.html. Bulk centroid ≈ (0.6002, 1.4198, 0.6000). RK4 glycolytic fold. Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.