Unified Survival-Constraint (USC) Framework v2: Deriving the Dark Sector from Janus-Boundary Entropy

The Unified Survival-Constraint (USC) framework is an upstream cosmological construction in which dark energy, dark matter, and late-time cosmic acceleration emerge from boundary geometry and entropy constraints rather than phenomenological parameter fitting. USC v2 derives the infrared density scale from entropy suppression at a CPT-symmetric Janus boundary, thereby fixing the characteristic scale of the cosmological constant, fixes the dark-matter mass scale via a geometric sparsity postulate, and predicts a late-time modification of the expansion history through a boundary-normalized activation invariant that does not insert the Hubble constant or acceleration redshift by hand. The framework is fully falsifiable, preserves early-universe observables, and yields a self-consistent late-time expansion history providing substantial partial relief to the Hubble and S₈ tensions within explicitly declared structural classes. This deposit contains the full USC v2 manuscript, the complete LaTeX source used to generate it, along with the source code implementing the MVND dynamical system (Section 8) and the raw simulation outputs validating the reported baseline results (including H₀USC = 72. 5 km/s/Mpc), enabling independent verification of the framework’s numerical implementation.