fix(v1.0.1): VDE-016 root cause + VDE-017 submodule path

VDE-016 (High): GCC two-phase lookup — root cause is anonymous namespace
- Move SSICurveData OUT of anonymous namespace into vde::brep
- Add #include <iterator> for std::begin/end
- Add using vde::brep::ClassResult

VDE-017 (Medium): Root CMakeLists configure_file CMAKE_SOURCE_DIR
- Change to CMAKE_CURRENT_SOURCE_DIR for submodule compatibility

src/brep/ssi_boolean.cpp

@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <cmath>
 #include <cstdint>
+#include <iterator>
 #include <limits>
 #include <map>
 #include <mutex>
@@ -40,6 +41,17 @@ using core::AABB3D;
 AABB3D face_bounds(const BrepModel& body, int face_id);
 Vector3D face_normal(const BrepModel& body, int face_id);
 struct SSICurveData;
+using vde::brep::ClassResult;
+
+/// SSI curve data for a face pair
+struct SSICurveData {
+    int face_a;
+    int face_b;
+    std::vector<Point3D> points;
+    Vector3D cutting_normal;
+    Point3D cutting_center;
+    bool valid = false;
+};
 
 namespace {
 
@@ -54,16 +66,6 @@ BrepModel extract_face_fragment(const BrepModel& body, int face_id);
 ClassResult classify_point_adaptive(
     const BrepModel& body, const Point3D& p, int& num_exact_upgrades);
 
-/// SSI curve data for a face pair
-struct SSICurveData {
-    int face_a;
-    int face_b;
-    std::vector<Point3D> points;       ///< 3D intersection points
-    Vector3D cutting_normal;           ///< best-fit plane normal for splitting
-    Point3D cutting_center;            ///< centroid of intersection points
-    bool valid = false;
-};
-
 // ═══════════════════════════════════════════════════════════
 //  Mesh caching (shared with brep_boolean.cpp pattern)
 // ═══════════════════════════════════════════════════════════