HγC O6: Bounded Closure of Calibration Logic for Structured Near-Critical Populations in Galactic Phenomenology

This paper establishes the bounded-closure layer for structured near-critical populations in galactic phenomenology within the HγC framework. Earlier N-series work established that the coarse-graining descriptor γ may be dynamically self-selected into a finite near-critical band, while O1, O2, and O3 stabilized the galactic diagnostic morphology, comparative morphology, and comparative estimator layers. O4 and O5 then established narrower comparative calibration and cross-contrast calibration consolidation. O6 takes the next justified step by asking whether the consolidated calibration logic can now sustain bounded closure for the Track A galactic line. The comparative estimator bundle composed of comparative center, comparative breadth, comparative asymmetry, and tail-supported persistence is reconsidered not merely as a cross-contrast calibration object, but as a structured closure object. On this basis, the paper distinguishes closure-bearing support, closure-compatible bounded residue, and contained versus proliferating tension. The closure proposed here is deliberately bounded. It does not claim exact convergence, catalogue-level precision fitting, galaxy-by-galaxy hidden-population reconstruction, or unique inversion from observed residual organization to realized γ-distributions. Instead, O6 argues that bounded closure becomes legitimate when support, neutral variation, and tension have become sufficiently differentiated in role, extent, and compatibility for the Track A galactic calibration logic to be stated in boundedly closed form. The paper does not complete the full observational programme of the HγC framework, nor does it enter later Track B comparison with the weak-field geometric, projected-profile, or lensing-side branches. Its role is narrower but decisive: if O4 established narrower calibration and O5 established calibration consolidation, O6 establishes bounded closure and prepares the mature handoff from the Track A galactic line to later cross-branch comparison.