Thin Extrude builds walls of a set thickness along sketch curves, open chains and closed loops, with the wall centred, inside, outside or on both sides at two thicknesses. Saved under format 20 (thin on an Extrude); an extrude without thin saves as before. Closes#721.
Adds oracle case 81 (a box edge rounded at a clamped cubic B-spline radius) with analytic expected values, and passes spline fillets through recipes.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Lasse Lian