forked from 1b-agent/opencadstudio-upstream
fit_spline_polyline bailed to a straight chord below three fit points, ignoring the stored begin/end tangents — a short tangent-clamped spline rendered as a line. The C² solver handles n=2 as-is (both end rows are clamp or natural conditions), so only the guard drops to n<2; tangentless two-point splines still solve to the straight chord. Co-Authored-By: Claude Fable 5 <[email protected]>