fix: S9 测试 namespace 修复 (core→vde) + unused variable 消除

tests/mesh/test_delaunay_3d.cpp

@@ -3,7 +3,7 @@
 #include <cmath>
 
 using namespace vde::mesh;
-using core::Point3D;
+using vde::Point3D;
 
 // ── Helper: compute circumsphere center and radius of 4 points ──
 // Returns (center, radius_squared). If points are coplanar, radius_sq < 0.
@@ -53,6 +53,7 @@ static bool verify_empty_circumsphere(
         if (r2 < 0.0) continue; // degenerate
 
         double r = std::sqrt(r2);
+        (void)r;  // explicitly unused, computed for potential debugging
         for (const auto& pt : input_points) {
             // Skip vertices of this tetrahedron
             double d2 = (pt - center).squaredNorm();