Electroweak masses and CP violation from the boundary

The boundary wave framework is extended from fermions to electroweak gauge bosons and CP violation. The weak mixing angle sin²θ_W = 2/9 follows from counting quark modes on the orbifold interval. Combined with the Sirlin relation and standard electroweak loop corrections, this predicts M_Z = 91.33 GeV (+0.16%) and M_W = 80.55 GeV (+0.22%) with M_Z as a prediction, not an input. The top Yukawa coupling y_t = 1 − (1/5)³ (0.08%) and Higgs quartic λ = (1 + (1/5)²)/8 (0.5%) emerge from the same perturbation hierarchy. Real overlap integrals give θ_QCD = 0 without a Peccei-Quinn symmetry; SU(2)_L doublet rotations at orbifold nodes generate δ_CP = arctan(m_d/m_u) = 65.0° (−0.12σ) and the Jarlskog invariant J = 2.99 × 10⁻⁵ (−0.6σ) — a structural Nelson-Barr mechanism requiring no additional fields. Fourth paper in a series deriving Standard Model observables from N_c = 3 and boundary geometry. ---Boundary Wave Framework Series (all submitted to Physical Review D):1. One formula for all fermion masses — https://zenodo.org/records/195787572. Decoherence spectrum of the Standard Model — https://zenodo.org/records/195787963. Fermion generations as standing wave nodes — https://zenodo.org/records/195788674. Electroweak masses and CP violation — https://zenodo.org/records/195789295. Strong sector, confinement, and hadron masses — https://zenodo.org/records/19579136