PHYSIQUE COSMIQUE VIVANTE Série IX — Validation expérimentale & tests discriminants Tests gravitationnels de la loi Φ_H Cadre méthodologique, test canonique S2 et cohérence inter-systèmes

This volume defines a fully explicit and falsifiable experimental framework for testing the relational law Φ_H in the gravitational domain. It does not report new observational results. Its purpose is methodological: to specify what is tested, how it is tested, and under which criteria a decisive experimental verdict can be reached. The framework introduces a minimal, parameter-locked prediction based on a dimensionless relational quantity Φ_H, constructed from standard observables, and calibrated exclusively in the weak-field regime. A single canonical test is identified: the orbital precession of the star S2 around Sagittarius A*. All other systems (S-stars, binary pulsars, GNSS clocks, time-delay lenses) are explicitly classified as coherence or compatibility tests. The volume provides a complete protocol, pipelines, limitations, degeneracies, and a standardized reviewer checklist, ensuring reproducibility and protection against post hoc reinterpretation. This work constitutes a methodological entry point to experimental confrontation, not a claim of validation.