What Eisenstein Was Tracking

Framework presupposed. We apply the established Bootstrap framework — S³/2I as the spacetime manifold (Paper 115); the spectral floor λ₁ = 168 with its icosahedral semigroup S(12, 20, 30) (Papers 117, 158, 174); the diagnosis that algebra is a 1D medium for 3D content (Paper 181); the quintic filter as A₅-insolvability mechanism with cohomology as its operational output (Papers 132, 215, 219); and the achiral substrate as the observer's address (Paper 176) — to the load-bearing 19th-century apparatus: the Eisenstein–Dedekind structure. Geometric spine and prime stratification. The closure ladder e^(α⁻¹) → e^(α⁻¹+5) → e^(α⁻¹+5+42) provides the geometric spine, with rung spans 5 = v (vertex degree) = E/D! (edges…