feat(v3.2): assembly tree + benchmark report + CI/Python/3MF

tests/brep/CMakeLists.txt

@@ -6,3 +6,4 @@ add_vde_test(test_brep_boolean)
 add_vde_test(test_brep_validate)
 add_vde_test(test_iges_import)
 add_vde_test(test_iges_export)
+add_vde_test(test_assembly)

tests/brep/test_assembly.cpp

@@ -0,0 +1,45 @@
+#include <gtest/gtest.h>
+#include "vde/brep/assembly.h"
+#include "vde/brep/modeling.h"
+
+using namespace vde::brep;
+using namespace vde::core;
+
+TEST(AssemblyTest, CreateEmpty) {
+    Assembly assy("test");
+    EXPECT_EQ(assy.name, "test");
+    EXPECT_EQ(assy.part_count(), 0u);
+}
+
+TEST(AssemblyTest, AddPart) {
+    Assembly assy("test");
+    auto box = make_box(2, 2, 2);
+    assy.root.add_part("box1", box);
+    EXPECT_EQ(assy.part_count(), 1u);
+    EXPECT_EQ(assy.node_count(), 2u); // root + box
+}
+
+TEST(AssemblyTest, NestedHierarchy) {
+    Assembly assy("robot");
+    auto* base = assy.root.add_part("base", make_box(10, 5, 2));
+    auto* arm = assy.root.add_subassembly("arm");
+    arm->add_part("seg1", make_cylinder(1, 8));
+    arm->add_part("seg2", make_cylinder(1, 6));
+    
+    EXPECT_EQ(assy.part_count(), 3u);
+    EXPECT_EQ(assy.node_count(), 4u); // root + arm + seg1 + seg2
+}
+
+TEST(AssemblyTest, VisitPartsWithTransform) {
+    Assembly assy("test");
+    assy.root.add_part("p1", make_box(1, 1, 1));
+    
+    size_t visited = 0;
+    assy.visit_parts([&visited](const std::string& name, const BrepModel&,
+                                 const Transform3D& xform) {
+        EXPECT_EQ(name, "p1");
+        EXPECT_TRUE(xform.isApprox(Transform3D::Identity()));
+        visited++;
+    });
+    EXPECT_EQ(visited, 1u);
+}