Radical-pair factorised yield: <Phi_s>_(theta,t) = <f>_theta * <g>_t (Fubini product-measure)

Radical-pair yield factorisation via Fubini. From framework F9 (Schulten-Weller Hamiltonian with separable angular and kinetic dependence), the double-averaged singlet yield over field orientations theta in [0, 2*pi) and lifetime t in [0,…