CDN-299: The Replay Harness

CDN-299 turns the CDN-298 replay packet into a deterministic replay harness. The harness validates packet admissibility, routes null controls and wall tracers away from low-drive amplitude fitting, then applies covariance-weighted model comparison to analysis-ready packets. A frozen seven-packet assay returns two signed-radial passes, one speed-even kill, one null pass, one null fail, one wall tracer, and one quarantine. This is not a spacecraft detection claim; it is the locked replay machinery future flyby-band Channel-B claims must pass.