V.T170 — Baryogenesis Exponent 15 = dim(τ³) × |generators|

The exponent 15 in η_B = α·ι_τ¹⁵·(5/6) equals dim(τ³) × |generators| = 3 × 5 = 15. Here dim(τ³) = 3 is the dimension of the fibered product τ³ = τ¹ ×_f T² (two fiber directions plus base), and |generators| = 5 is the count of generators {α, π, γ, η, ω}. The same dimensional structure appears in the neutrino mass sector (Sprint 2A).