The Microphysical Origin of the Hubble Tension: Geometric Aliasing and the Substrate Derivation for Thermodynamic Cosmology

The persistent 5 sigma discrepancy between local and primordial measurements of the Hubble constant ($H_0$) points to a fundamental incompleteness in the $\Lambda$CDM model, suggesting that cosmological dynamics are not scale-invariant. While recent Thermodynamic Gravity (TRG-CGR) approaches correctly describe cosmic acceleration as a horizon entropy maximization phenomenon, they lack a definition of the microscopic substrate that carries these degrees of freedom. In this work, we resolve this ontological deficit by applying the framework of General Relativity as a Quantum Theory (GRQT). By formalizing spacetime as a Covariant Sampling Lattice subject to a finite Geometric Impedance ($\alpha$), we demonstrate that the expansion of the universe induces a regime transition in the spatial resolution of the causal graph. We analytically derive that the node update rate in the late universe undergoes geometric aliasing effects due to the holographic constraint of the Hubble surface. This results in a scale-dependent correction of the form $H_{obs} \approx H_{int} + \mathcal{O}(\alpha/R)$, which reproduces the phenomenological $1/R$ law without introducing new fields or dark energy fluids. We conclude that the Hubble Tension is not an observational failure, but the spectral signature of spacetime granularity and the bulk viscosity of the quantum vacuum.