fix: 统一使用 using namespace vde::core 引入 Point3D/Vector3D

tests/boolean/test_boolean_mesh.cpp

@@ -5,7 +5,7 @@
 
 using namespace vde::boolean;
 using namespace vde::mesh;
-using vde::core::Point3D;
+using namespace vde::core;
 
 // ── Helper: build a box mesh (12 triangles, 8 vertices) ──
 // Face normals point outward (CCW winding from outside)

tests/brep/test_brep.cpp

@@ -4,8 +4,7 @@
 #include <cmath>
 
 using namespace vde::brep;
-using vde::core::Point3D;
-using vde::core::Vector3D;
+using namespace vde::core;
 
 // ═══════════════════════════════════════════════════════════
 //  Basic entity creation (box, sphere, cylinder)

tests/mesh/test_delaunay_3d.cpp

@@ -3,7 +3,7 @@
 #include <cmath>
 
 using namespace vde::mesh;
-using vde::core::Point3D;
+using namespace vde::core;
 
 // ── Helper: compute circumsphere center and radius of 4 points ──
 // Returns (center, radius_squared). If points are coplanar, radius_sq < 0.