Topological Origin of the Fine-Structure Constant from Spinor Transport Closure

We derive the fine-structure constant α−¹ = 137. 036 from geometric consistency requirements of a Finsler–Randers substrate. The key result is a Spinor Transport Closure Theorem: a spacetime supporting globally consistent spin-1/2 transport must satisfy the structural identity κnbare = 1, where nbare is the density of minimal transport loops and κ is the normalized Randers flag curvature. The integer nbare = 24 is derived from the dimensionality, orientation structure, and transverse curvature modes of spin transport in four dimensions. A topological instanton associated with gradient relaxation then fixes the electromagnetic coupling, yielding α = 2C/e^π²/2, where C = 1. 014667 is a one-loop determinant computed using the Gel’fand–Yaglom method. No free parameters or fitted constants appear.