A Strong-Field Observability Rubric for Modified Gravity: From Formal Wave Solutions to Binary-Merger Predictions Case Study: Spin-1 Hamiltonian Composite Gravity

This manuscript proposes a strong-field observability rubric for modified and alternative theories of gravity. The rubric is designed to distinguish formal mathematical structures - such as wave equations, static metrics, or linear perturbations - from observationally closed binary-merger predictions. It complements weak-field frameworks such as the parametrized post-Newtonian formalism by specifying the additional source-native closure chain needed for gravitational-wave claims: matter coupling, detector response, native radiation flux, low-order radiation cancellation or bounds, inspiral phasing, ringdown spectra, causal propagation, and quantum closure when quantum stability is claimed. The paper calibrates the rubric against the classical general-relativistic binary-merger program and explicitly scopes the rubric as an inductive, source-native closure checklist rather than a theorem or replacement for weaker exploratory tools. The rubric is then applied as a case study to a recent Hamiltonian composite theory of gravitation built from tetrads and Lorentz Yang-Mills-type gauge fields. The case-study theory constructs an effective metric from tetrads, interprets planar gravitational waves as spin-1 gauge-vector modes, and presents a static black-hole-like solution with tetrad sign reversal. The audit finds that strict application of the rubric halts at the matter-coupling milestone: the source theory does not derive the matter action or test-mass response needed to convert field variables into detector motion. Downstream milestones remain open, including native compact-binary flux, low-order vector-radiation cancellation or bounds, inspiral phasing, ringdown quasi-normal modes, tetrad causality, and Ward-identity/quantum closure. The result is not a falsification claim. It is a closure classification: the case-study theory has not yet earned binary-merger observability under the proposed rubric. The manuscript includes an appendix giving a conditional tetrad-to-strain map, explicitly quarantined as a hypothetical downstream result that applies only if matter coupling is later closed by a metric-response law. Files Included: main_v100.pdf — Final compiled manuscript. main_v100.tex — REVTeX 4.2 source file. strong_field_rubric_v100_release.zip — Reproducibility bundle containing the compiled PDF, LaTeX source, compile report, SHA256 checksums, and rendered PDF contact sheet.