Electron Mass from 10-Dimensional Geometric Coupling: A Prediction from the 5+5+1 Unified Framework

We show that the electron mass can be expressed as m_e = M_P · α¹⁰ · sin²(π/10) · φ^(1/20), yielding 9.104 × 10⁻³¹ kg—within 0.06% of the observed value. Each factor has geometric interpretation: α¹⁰ from coupling suppression through 10 dimensions, sin²(π/10) = φ²/4 from pentagon symmetry, and φ^(1/20) from boundary energy distribution across 20 coupling modes. Extended to muon (0.2% error), tau (0.3% error), and neutrino masses (~0.07 eV prediction). Zero free parameters. Spinoff from: "Unified Theory: Complete Derivation of Physics from 5+5+1 Dimensional Geometry" (DOI: 10.5281/zenodo.18133453)