内螺纹 thread_cut 算子的增加

backend/engine/cdsl_engine/runtime.py

@@ -24,7 +24,7 @@ ALL_ATOMIC_IDS = frozenset({
     "revolve_add", "revolve_cut", "hole_blind", "hole_countersink",
     "hole_counterbore", "sphere_add", "reference_plane", "reference_axis",
     "hole_wizard", "fillet", "chamfer", "pattern_linear", "pattern_mirror",
-    "thread_add",
+    "thread_add", "thread_cut",
 })
 
 
@@ -525,11 +525,28 @@ def _execute_thread(node: FeaturePlanNode, session: ExecutionSession) -> Feature
 
 
 def _thread_executor(node: FeaturePlanNode, session: ExecutionSession, sketch: dict[str, Any] | None) -> FeatureResult:
-    # 螺纹不需要草图平面，丢弃该参数后执行。
+    # 螺纹特征（thread_add/thread_cut）不需要草图平面，丢弃该参数后执行。
+    # thread_cut 走布尔差分支：从已有主体切出内螺纹槽，而非并入外螺纹段。
     del sketch
+    if node.atomic_id == "thread_cut":
+        return _execute_thread_cut(node, session)
     return _execute_thread(node, session)
 
 
+def _execute_thread_cut(node: FeaturePlanNode, session: ExecutionSession) -> FeatureResult:
+    # 内螺纹（thread_cut）执行入口：ThreadSpec.from_feature 对 thread_cut 恒置
+    # internal=True，生成牙顶外放 INTERNAL_CUT_OVERLAP_MM 的切削刀具，沿
+    # spec.axis 放置后从当前主体布尔差出全深螺旋牙槽（宿主通常已预打光孔，
+    # 刀具 core 落在孔腔中，仅外放的牙槽层切入孔壁）。
+    # 1. 解析并校验尺寸/牙距/轴，非法输入抛出带具体原因的 ValueError。
+    spec = ThreadSpec.from_feature(node.atomic_id, node.params)
+    # 2. 由适配器门面生成沿 spec.axis 放置的内螺纹切削刀具实心段。
+    tool = session.adapter.thread_solid(spec)
+    # 3. 从当前主体布尔差（cut）后登记为新主体，并返回该特征的结果对象。
+    session.register_body(node.feature_id, session.adapter.cut(session.body, tool), replay_node=node)
+    return session.result(node)
+
+
 def _host_plane(resolution: SelectorResolution) -> PlaneSpec:
     if resolution.record is None:
         raise ValueError(resolution.diagnostic.message if resolution.diagnostic else "host face was not resolved")
@@ -1042,6 +1059,7 @@ EXECUTORS: dict[str, ExecutorFunction] = {
     "reference_axis": _reference_axis_executor,
     "sphere_add": _sphere_executor,
     "thread_add": _thread_executor,
+    "thread_cut": _thread_executor,
     "extrude_add_blind": _primary_executor,
     "extrude_add_two_sided": _primary_executor,
     "extrude_cut_blind": _primary_executor,