Chapter 70: The Mass Ratio R and the 10-Link Chain

The neutron-to-electron mass ratio R = m_n / m_e ≈ 1838.684 is derived from ι_τ through a chain of exactly 10 links—each τ-effective, with zero conjectural ingredients. This chapter presents the complete chain from start to finish: from the τ³ fibration (Book I) through the Epstein zeta function and lemniscate capacity to the final comparison with CODATA. The result is a first-principles derivation of the electron mass to sub-ppm precision.