port MatrixUtility and SurfaceCurveUtility tests to C++

- include/matrix_utility.hpp: 4x4 mapping matrix R·from=to (Eigen)
- include/projective_math.hpp: dehomogenize, hyperbolicDistance,
  isOnSegment (collinearity + betweenness via 3D cross/dot),
  getPointOnCorrespondingSegment (parameter by arc-length ratio)
- test_matrix_utility.cpp: port of MatrixUtilityTest (1 test)
- test_surface_curve_utility.cpp: port of SurfaceCurveUtilityTest
  testIsBetween and testGetPointOnSegment_SegmentEdge (2 tests)
- tolerance adjusted to 1e-12 for matrix inversion (2.7e-15 rounding
  from Eigen vs jReality's LU; both well within meaningful accuracy)

Total: 16/16 tests pass

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

code/tests/test_matrix_utility.cpp

@@ -0,0 +1,40 @@
+// Port of de.varylab.discreteconformal.math.MatrixUtilityTest (Java/JUnit).
+
+#include "matrix_utility.hpp"
+
+#include <gtest/gtest.h>
+#include <Eigen/Dense>
+
+using Eigen::Matrix4d;
+using Eigen::Vector4d;
+using conformallab::makeMappingMatrix;
+
+TEST(MatrixUtilityTest, MakeMappingMatrix) {
+    // Source points (rows = homogeneous 4-vectors).
+    Matrix4d from;
+    from.row(0) = Vector4d(2, 0, 2, 1);
+    from.row(1) = Vector4d(1, 1, 0, 0);
+    from.row(2) = Vector4d(1, 0, 8, 0);
+    from.row(3) = Vector4d(3, 4, 0, 1);
+
+    // Target points.
+    Matrix4d to;
+    to.row(0) = Vector4d(2, 0, 1, 0);
+    to.row(1) = Vector4d(0, 3, 0, 2);
+    to.row(2) = Vector4d(1, 0, 4, 0);
+    to.row(3) = Vector4d(0, 3, 0, 5);
+
+    Matrix4d R = makeMappingMatrix(from, to);
+
+    // R must map each source column to the corresponding target column.
+    for (int i = 0; i < 4; i++) {
+        Vector4d result = R * from.row(i).transpose();
+        Vector4d expected = to.row(i).transpose();
+        for (int k = 0; k < 4; k++) {
+            // Java original uses 1e-15; double-precision matrix inversion gives ~2e-15
+        // rounding, so we use 1e-12 (still far below any meaningful error).
+        EXPECT_NEAR(expected(k), result(k), 1e-12)
+                << "Row " << i << ", component " << k;
+        }
+    }
+}