Part 6B: Structural Derivation of the Bulk–Boundary Inertial Hierarchy Baseline - From Global (H_4) Root Participation to the Golden-Ratio Conjugate Separation Norm

Part 6 of the Origin Geometry (OG) program introduced two candidate geometric hierarchy baselines emerging from discrete H₄ geometry: I_int = 20ϕ⁴ and R_bb = 120√5ϕ⁴. Part 6A provided a structural derivation of the first expression, I_int = 20ϕ⁴, by interpreting 20 as the local icosahedral interface-channel count and ϕ⁴ as the four-dimensional golden-ratio support measure. The present Part 6B addresses the second expression, R_bb = 120√5ϕ⁴, and argues that it is a structurally preferred bulk–boundary inertial hierarchy baseline within the OG framework. We show that the factor 120 arises from the global H₄ root participation multiplicity, corresponding to the 120 roots of the H₄ root system and the 120 vertices of the 600-cell. The factor ϕ⁴ is inherited from the four-dimensional golden-ratio support measure established in Part 6A. The remaining factor, √5, is interpreted as the golden-ratio conjugate separation norm, |ϕ - ϕ̅| = √5, where ϕ̅ is the algebraic conjugate of ϕ. Within the OG bulk–boundary interpretation, this conjugate gap is proposed as the intrinsic metric separation factor between bulk-supported and boundary-projected participation classes. The resulting expression R_bb = 120√5ϕ⁴ ≈ 1839.15 lies close to the observed proton–electron mass ratio. This numerical proximity is structurally suggestive, but it is not interpreted as a derivation of proton mass, electron mass, QCD confinement, or hadronic binding energy. Rather, R_bb is proposed as a pre-dynamical inertial hierarchy baseline that may later be dressed by binding, screening, and collective relaxation effects.