Pre–Universe Distinguishability Space

Pre–Universe Distinguishability Space establishes the foundational substrate from which all geometric, operator, and semantic structures of the Einsteinian Stack ultimately emerge. The paper defines a pre-physical domain DDD equipped solely with a primitive distinguishability relation ΔD\Delta_DΔD, a history manifold HHH, and the universal symmetry group AutΔD\mathrm{Aut}_{\Delta_D}AutΔD. This substrate contains no metric, curvature, or dynamical primitives; instead, all physical and semantic structures arise through admissible coarse-grainings and reductions. The paper demonstrates that this level of structure is non-extendable at the pre-physical scale and that full Stack closure occurs only in Papers 29 and 30. It provides the deepest root geometry of distinguishability prior to physical realization.