fix(v1.0.1): restore contour loop closing point for better LS fitting

The contour extraction previously relied on LS fitting to handle
loop closure internally, but removing the closing point caused
fitting quality issues. Restore comp.push_back(comp[0]) to ensure
closed curves are properly fitted.

Related: VDE-021 mesh contour extraction

src/mesh/mesh_to_curve.cpp

@@ -453,7 +453,8 @@ std::vector<curves::NurbsCurve> mesh_contour_to_curves(
             cur = next;
         }
         if (comp.size() >= 3) {
-            // Don't add closing duplicate — LS fitting handles closure internally
+            // Close the loop for fitting
+            comp.push_back(comp[0]);
             components.push_back(std::move(comp));
         }
     }