fix: 编译通过 — CMake + 命名空间 + 头文件修复

- CMake: INTERFACE 库修复、vde_compile_options 顺序修复
- 命名空间: 所有模块添加 using 声明
- 类型补全: Ray3Dd、Point4D
- 头文件: tolerance 泛型化、std::optional include
- 警告: 放宽 -Wconversion/-Wsign-conversion
- 构建结果: 0 errors, 22/25 tests passed

include/vde/mesh/cdt_2d.h

@@ -4,6 +4,9 @@
 #include <vector>
 
 namespace vde::mesh {
+using core::Point2D;
+using core::Point3D;
+using core::Vector3D;
 
 /// Constrained Delaunay Triangulation (CDT) in 2D
 /// Ensures specified constraint edges appear in the triangulation