Tow-Hitch Ball Wear Limit (<49.0mm ISO) & 50mm vs 2-Inch vs 1-7/8" Mismatch Guard

Deterministic ID-1 homography + sub-pixel polar ellipse fit of sphere silhouette (equatorial vs fore-aft wear chord) with 47.63 / 50.00 / 50.80 mm classification engine (.jpg, .heic, .png, .pdf) built for Westfalia, AL-KO, Brink / Thule, Curt Towing — zero-upload ephemeral Wasm RAM execution.