A Structure-Dependent Route to Cosmic Acceleration in Zero Theory Time-Sink, Hydrogen Clocks, and Compensated Spacetime Structure

This manuscript (v2.1) develops a Zero Theory proposal in which electron-associated outward fountain presentation and proton-associated inward Time-Sink connect hydrogen centre-environment structure to a conditional route for late-time cosmic acceleration. It separates fundamental Zero, pregeometric Structured Zero, and compensated effective straightness; derives conditional volume-partition identities for disjoint regions compared under one declared time; and situates the proposal relative to relativistic averaging, Timescape clock calibration, backreaction constraints, and observational tests. The Oort projection and hydrogen-frequency benchmark retain their declared inputs and are not used to set a cosmological parameter. No independent dark-energy substance is added, and no derived cosmic expansion history or observational validation is claimed.