Kinematic Coherence in the Milky Way Halo: Pipeline Design, Mock Validation Protocol, and Gaia DR3 Implementation RCD Paper XXIV-b

We extract a kinematic coherence length L_KC from the Gaia DR3 six-dimensional halo sample (N=3704 stars) using a stability-filtered marked-pair velocity correlation estimator. Two independent binning schemes yield a consolidated empirical scaling L_KC ≈ (0.11 ± 0.02) r_GC. Eighty null realizations produce zero valid L_KC(r) slopes. Correlation with chi_C(r) from Papers XIV-XVII is positive, but BIC model comparison does not favor the structural model over a simple radial null, triggering kill switch KS-4. The kinematic coherence scaling is observationally established but does not yet receive positive structural support.