Spiral arms in disk galaxies are often modeled as density waves or long-lived stellar structures. This paper tests a Holosphere Theory alternative: spiral arms as standing admissibility patterns, meaning persistent coherence ridges in a rotating lattice that organize visibility and transport without requiring fixed material membership. Using public SPARC disk-scale metadata and public Pan-STARRS1 (g/r/i) imaging, we implement an audit-grade KPI decision contract with a strict hierarchy: (1) an Applicability Gate (AG) that determines whether a coherent ridge domain is detectable under the declared pipeline, (2) a Coherence Ordering Signal (COS) measured only for AG-pass galaxies via segment-resolved cross-arm optical ordering in pixel space, and (3) a demonstrator-only Domain Transition Anchor (DTA) testing whether the ordering transition is anchored to the exponential disk scale length Rd. Under this contract, cross-arm ordering is conditional and is evaluated only when a ridge domain exists. In the demonstrator galaxy UGC09133, COS is detected across independent ridge segments and the ordering transition is anchored to the outer spiral domain at approximately greater than or equal to 3Rd. These results establish existence and disk-scale anchoring of a coherence-gated ordering proxy under a fully declared public-data pipeline, providing a foundation for follow-on papers that quantify prevalence, test pattern-speed implications, and extend to multi-timescale tracers.