fix(v1.0.3): 修复 get_face_index_by_position 中 face_centroid 作用域错误

face_centroid 定义在 ssi_boolean.cpp 中，不在任何头文件中声明，
改为在 get_face_index_by_position 中内联计算面质心。

src/brep/modeling.cpp

@@ -1230,8 +1230,16 @@ int get_face_index_by_position(const BrepModel& body, const Point3D& nearPoint)
     int best_id = -1;
     double best_dist = std::numeric_limits<double>::max();
     for (size_t fi = 0; fi < body.num_faces(); ++fi) {
-        // Use face bounds center as reference point
-        Point3D center = face_centroid(body, static_cast<int>(fi));
+        // Compute face centroid from its edge vertices (same as face_centroid in ssi_boolean.cpp)
+        auto edges = body.face_edges(static_cast<int>(fi));
+        Point3D center(0, 0, 0);
+        int count = 0;
+        for (int ei : edges) {
+            const auto& e = body.edge(ei);
+            center += body.vertex_by_id(e.v_start).point; count++;
+            center += body.vertex_by_id(e.v_end).point; count++;
+        }
+        if (count > 0) center = center / static_cast<double>(count);
         double d = (center - nearPoint).norm();
         if (d < best_dist) { best_dist = d; best_id = static_cast<int>(fi); }
     }