Co-ports SmFindCurveDistanceExtremaEFO::Evaluate (curve.curve_p4) and
SmCurve::IsLine (curve.curve_p5, B-spline body); wires the curve span
back-edges of curve.curve_p2 and geom.tree, and the IsLine stub of
nurbs.b_spline_curve_p2. Difftest: 638 cases, 3 deferred.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V8ohWGLCzFPoZriCeSSero
bherbruck