fix(engine): 保留并正交化平面 y_dir 方向

backend/engine/cdsl_engine/runtime.py

@@ -702,9 +702,20 @@ def _mirrored_node(node: FeaturePlanNode, instance_id: str, plane: PlaneSpec) ->
         host_frame.get(key) is not None for key in ("origin_mm", "x_dir", "normal")
     )
     if positions_are_local:
-        for key in ("origin_mm", "x_dir", "y_dir", "normal"):
+        for key in ("origin_mm", "x_dir", "normal"):
             if host_frame.get(key):
                 host_frame[key] = _reflect_point(host_frame[key], plane, vector=key != "origin_mm")
+        # #1 y_dir 保留：PlaneSpec 现在会尊重显式正交 y_dir。镜像后 frame 的
+        # canonical y 轴必须是 n×x（x 已反射 → y 反转），否则反射后的 frame
+        # 会保留反射前的 y_dir，与下方"局部坐标 v 取反"双重翻转。
+        x_reflected = host_frame.get("x_dir")
+        n_reflected = host_frame.get("normal")
+        if x_reflected is not None and n_reflected is not None:
+            host_frame["y_dir"] = [
+                n_reflected[1] * x_reflected[2] - n_reflected[2] * x_reflected[1],
+                n_reflected[2] * x_reflected[0] - n_reflected[0] * x_reflected[2],
+                n_reflected[0] * x_reflected[1] - n_reflected[1] * x_reflected[0],
+            ]
         # See _mirrored_sketch: the canonical reflected plane reverses local
         # y, so local hole coordinates must do the same.
         for position in params.get("positions") or []: