GDUM: A Substrate-Free Readout-Type Quantum Gravity Framework Based on the ℤ₂-Conjugate Double-Sheeted Covering

We propose GDUM (ℤ₂-Conjugate Double-sheet Unfolding Model), a background-independent, relation-based quantum gravity framework with no underlying substrate. The model takes only the Layer 0 ℤ₂ involutive conjugate relation as its unique ontological primitive; spacetime, geometry, fields, fundamental constants, and the laws of thermodynamics are all emergent appearances (Layer 2), generated through the double-sheeted covering, Deck transformations, and the readout map. The Planck scale is the applicability threshold of the classical spacetime appearance rather than an ontologically discrete unit; the vacuum speed of light is the steady-state maximum propagation velocity of the readout channel in the low-residual regime; entropy increase is interpreted as the sedimentation of conjugate distinction-information into the Layer 0 ontological sink; and the gravitational singularity is not a coordinate artifact but an intrinsic critical failure interface of the readout map, where the second-order homotopy obstruction kernel K⁽²⁾ switches from a tiny residual to the dominant physical contribution. Without introducing any vacuum-energy entity, the model reproduces the observed effects of the dark sector: the primordial cosmic interface and the black-hole singularity share the same K⁽²⁾ obstruction kernel, providing a cross-scale falsifiable observational fingerprint. In the low-residual macroscopic limit, the framework automatically reduces to general relativity and classical thermodynamics. This paper strictly distinguishes ontological meta-theoretical interpretation from falsifiable physical predictions; the full quantum realization of the topological field equations and the obstruction kernel is recorded as an open problem.