Structural Constant Readouts: Fine-Structure and Mass-Ratio Candidates from Finite Distinguishability Closure

Structural Constant Readouts (SCR) is a companion paper to Phase-Flow Coherence (PFC v5). While PFC establishes the quantum representational architecture associated with Finite Distinguishability Closure (FDC), SCR focuses on the physical reading of FDC numerical readouts as dimensionless constant candidates.The paper examines four parameter-free readouts produced by the FDC framework: a Route I scalar readout near the inverse fine-structure constant, and three Route II distributed readouts near the proton/electron, muon/electron, and tau/electron mass ratios. These readouts are treated as fine-structure- and mass-ratio-like candidates, not as completed derivations of the Standard Model.The logical status is explicitly conditional. SCR does not claim to derive electromagnetism, particle species classification, gauge representations, mass generation, or the full Standard Model. Instead, it records a central physical reading hypothesis: that the same finite closure structure which grounds PFC's quantum representational architecture also produces dimensionless structural readouts close to several independent physical constants.A quantitative coincidence-cost estimate is included to clarify why the simultaneous appearance of four such readouts from one parameterless structure is not treated as mere numerology. The estimate is presented as an order-of-magnitude diagnostic, not as a rigorous Bayesian probability theorem.This work should be read together with PFC v5, DOI: 10.5281/zenodo.20069101, and the underlying FDC paper.