HγC O1: Diagnostic Morphology of Structured Near-Critical Bands in Galactic Phenomenology

This paper establishes the first explicitly galactic diagnostic morphology layer for structured near-critical bands in 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, that this band should be treated not as a featureless interval but as a structured mesoscopic distribution, and that its internal organization can be reformulated in observationally oriented diagnostic terms. O1 takes the next justified step by introducing a minimal descriptor set for the galactic sector: population center, width, asymmetry, and tail support. Within this framework, residual diversity is not treated as undifferentiated scatter around an otherwise exact law, but as the observable image of differently populated realizations of a shared near-critical regime family. The paper therefore stabilizes a diagnostic language in which common mean galactic behaviour and organized residual diversity can be compared without collapsing the problem back into mean-law competition alone. The scope of the paper is deliberately limited. O1 does not perform full catalogue-level fitting, derive the bridge-variable ensemble microscopically, derive the characteristic acceleration scale from first principles, enter the temporal and fluctuation-dependent reorganization sectors associated with the W-series, or integrate the galactic line with projected-profile morphology from the weak-field lensing branch. Instead, it fixes the diagnostic morphology layer that must precede later comparative morphology, estimator construction, and narrower calibration.