The standard ΛCDM cosmological model relies on dark sector phenomenologies that increasingly conflict with late-time observational constraints, most notably the S_8 matter-clustering anomaly. We introduce the Holographic Unspooling Framework (HUF), a zero-free-parameter geometric model that derives cosmic evolution directly from the thermodynamics of the cosmological horizon. By treating the missing 26.6% of the cosmic energy budget not as cold dark matter particles, but as Ω_info—the kinematic weight of macroscopic entanglement entropy (w=0)—we strictly preserve the acoustic peaks of the CMB and the BAO scales. The unspooling of this information drives a dynamic effective gravitational coupling (μ ≈ 0.9529 today) parameterized by the logarithmic Bekenstein-Hawking entropy. Solving the quasi-static modified growth equations yields S_8 = 0.763, cleanly resolving the tension with independent weak-lensing surveys (KiDS-1000 and DES Y3) without phenomenological tuning. We detail the framework's falsifiable predictions and identify the derivation of the decoherence transfer function (T_dec) for the A_lens anomaly as the primary open problem.