Arithmetic Expression Geometry I: Foundations

Paper I — Foundations.** Intrinsic sequential-tree classification, marked spinal histories, bilateral projective semantics, the affine sector, the `q=4` Hecke arithmetic sublanguage, regular-zero rigidity, singular arithmetic expression spaces, and the interfaces to the later papers. The affine cocycles, continuous flow, hyperbolic model, ACS torsion, and contact curvature developed in earlier versions of this paper now belong to Paper 0