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/engine/cdsl_engine/sketch_solver.py

@@ -1,9 +1,9 @@
 """Core CDSL sketch resolver.
 
 The runtime accepts only direct geometric descriptions: circles, straight-edge
-polygons, and closed analytic line/arc/circle contours.  Semantic shapes and
-historical profile macros belong to the importer compatibility layer and must
-be lowered before this module is invoked.
+polygons, and closed analytic line/arc/circle/B-spline contours. Semantic
+shapes and historical profile macros belong to the importer compatibility
+layer and must be lowered before this module is invoked.
 """
 
 from __future__ import annotations
@@ -81,6 +81,11 @@ def _transform_contours(contours: list[_Ctx], workplane: _Ctx) -> list[_Ctx]:
         if edge["type"] == "arc":
             output["center_mm"] = _to_3d(workplane, edge["center_mm"][0], edge["center_mm"][1])
             output["normal"] = list(normal)
+        elif edge["type"] == "bspline":
+            output["points_mm"] = [
+                _to_3d(workplane, point[0], point[1])
+                for point in edge["points_mm"]
+            ]
         transformed.append(output)
     return transformed
 
@@ -118,6 +123,8 @@ def _reverse(edge: _Ctx) -> _Ctx:
     output["start_mm"], output["end_mm"] = output["end_mm"], output["start_mm"]
     if output.get("type") == "arc" and "clockwise" in output:
         output["clockwise"] = not bool(output["clockwise"])
+    if output.get("type") == "bspline":
+        output["points_mm"] = list(reversed(output["points_mm"]))
     return output
 
 
@@ -163,7 +170,16 @@ def _segment_edges(segment: _Ctx) -> list[_Ctx]:
     if kind == "circle":
         return _circle_edges(segment)
     if kind == "bspline":
-        raise ValueError("analytic_contours: bspline requires an explicit approximation capability")
+        points = segment.get("points") or []
+        if len(points) < 3:
+            raise ValueError("analytic_contours: bspline needs at least 3 interpolation points")
+        converted = [_point(point) for point in points]
+        return [{
+            "type": "bspline",
+            "start_mm": converted[0],
+            "end_mm": converted[-1],
+            "points_mm": converted,
+        }]
     raise ValueError(f"analytic_contours: unsupported segment type {kind!r}")
 
 
@@ -172,6 +188,9 @@ def _sample_loop(edges: list[_Ctx]) -> list[tuple[float, float]]:
     for edge in edges:
         start = edge["start_mm"]
         points.append((float(start[0]), float(start[1])))
+        if edge.get("type") == "bspline":
+            points.extend((float(point[0]), float(point[1])) for point in edge["points_mm"][1:-1])
+            continue
         if edge.get("type") != "arc":
             continue
         center, end = edge["center_mm"], edge["end_mm"]