修改了一些之前增加功能的bug

backend/engine/cdsl_engine/parametric_thread.py

@@ -110,11 +110,12 @@ def _build_z_aligned(spec: ThreadSpec) -> Solid:
     # material; the crest centre sits at the helix start phase (z = 0), which
     # also puts the z = 0 end face through full crest material after trimming.
     helix_height = spec.length_mm + 2.0 * pitch
-    helix = Edge.make_helix(
-        pitch=pitch,
-        height=helix_height,
-        radius=root_radius,
-        lefthand=spec.lefthand,
+    # 复用 adapter 门面构造螺旋路径与扫掠。函数级延迟导入：build123d_adapter 顶部
+    # 已 import build_thread_solid，模块级反向 import adapter 会形成循环依赖。
+    from .build123d_adapter import Build123dGeometryAdapter
+
+    helix = Build123dGeometryAdapter.helix_path(
+        root_radius, pitch, height_mm=helix_height, lefthand=spec.lefthand,
     )
 
     # Profile vertices (z, r) -> world (x = r, y = 0, z).  Order is counter
@@ -130,7 +131,7 @@ def _build_z_aligned(spec: ThreadSpec) -> Solid:
     ]
     wire = Wire([Edge.make_line(pts[index], pts[(index + 1) % len(pts)]) for index in range(len(pts))])
     wire = _apply_profile_fillets(wire, spec, crest_radius, sunk_root, pitch, crest_half_width)
-    ribbon = Solid.sweep(section=Face(wire), path=helix, make_solid=True, is_frenet=True)
+    ribbon = Build123dGeometryAdapter.sweep(Face(wire), helix, make_solid=True, is_frenet=True)
 
     # Core cylinder at the nominal minor radius spanning the whole helix.
     # (The sunken tooth roots overlap it so the union below is clean.)