feat(cadfs): 补齐核心建模能力并建立代表性回归

- 新增 loft、双向切除、through-all/up-to-next 等 CADFS lowering 与 engine 支持
- 支持多种 reference plane、B-spline profile 和 circular pattern replay
- 保留 transform 历史，并烘焙安全的单源平移/旋转变换
- 改进 selector 绑定、拓扑快照和 pattern 变换处理
- 建立 17 个代表样本的转换、重建与比较回归工具链
- 补充 schema、author guidance、运行时和几何回归测试

backend/tests/test_engine_pattern_transform_contract.py

@@ -316,6 +316,55 @@ class PatternTransformContractTests(unittest.TestCase):
 
         self.assertAlmostEqual(rebuilt["volume_mm3"], 1000 + 72 + 24, places=5)
 
+    def test_circular_pattern_rotates_analytic_arc_normals_with_the_sketch(self) -> None:
+        """倾斜圆草图的环形阵列必须保持每条圆弧处于旋转后的工作平面。
+
+        ``analytic_contours`` 在运行时会预先展开为世界坐标的圆弧边。环形阵列
+        不能只旋转边端点和圆心：Build123d 依据 edge.normal 计算三点圆弧中点，
+        法向遗留在源草图平面会让中点偏离 wire 平面，最终报
+        ``Cannot build face(s): wires not planar``。该 fixture 使用绕 Z 轴的
+        垂直圆草图，保证每个实例都实际变换该法向。
+        """
+        cdsl = {
+            "schema": "cad.cdsl.llm.v1", "schema_version": "1.1.0", "kind": "part",
+            "part_id": "circular-arc-normal", "meta": {"unit": "mm"},
+            "geometry": {"sketches": [
+                {
+                    "id": "base", "workplane": _workplane(origin=[0, 0, 0], normal=[0, 0, 1]),
+                    "profile": {"type": "circle", "center": [0, 0], "radius_mm": 10},
+                },
+                {
+                    "id": "boss", "workplane": _workplane(origin=[0, -10, 0], normal=[0, 1, 0]),
+                    "profile": {"type": "analytic_contours", "contours": [{
+                        "role": "outer", "closed": True,
+                        "segments": [{"type": "circle", "center": [0, -5], "radius_mm": 1}],
+                    }]},
+                },
+            ]},
+            "features": [
+                {
+                    "id": "base_add", "atomic_id": "extrude_add_blind", "depends_on": [],
+                    "sketch_id": "base", "params": {"distance_mm": 10},
+                },
+                {
+                    "id": "boss_add", "atomic_id": "extrude_add_blind", "depends_on": ["base_add"],
+                    "sketch_id": "boss", "params": {"distance_mm": 2},
+                },
+                {
+                    "id": "repeat", "atomic_id": "pattern_circular", "depends_on": ["boss_add"],
+                    "params": {
+                        "source_feature_ids": ["boss_add"],
+                        "axis": {"origin_mm": [0, 0, 0], "direction": [0, 0, 1]},
+                        "pattern_count": 4, "sweep_angle_deg": 360,
+                    },
+                },
+            ],
+        }
+        with tempfile.TemporaryDirectory() as directory:
+            rebuilt = rebuild_cdsl(cdsl, Path(directory) / "circular-arc-normal.step")
+        self.assertGreater(rebuilt["volume_mm3"], math.pi * 1000)
+        self.assertEqual(rebuilt["solid_count"], 1)
+
 
 if __name__ == "__main__":
     unittest.main()