By: ValentinHirschi <valentin.hirschi@gmail.com>
correct contracted MATAD numerator orientations User request: Continue as planned, and summarize where you are at Retain denominator conventions and fix the signed parent-edge map for contracted three-loop loop bases. Preserve all existing assertions and add independent momentum identities, mixed-product and unit/nonunit-mass regressions. Fresh tests: 3 routing, 16 K6 pipeline, 15 AlphaLoop/MATAD comparisons; all pass. Independent audit reran all three selections. Native FeynKit/RustRed lanes retain invalid FORM paths. This is not a fresh rerun of the historical 83-test inventory or a four-loop acceptance claim.