feat(cadfs): expand selector provenance coverage

backend/engine/cdsl_engine/executors/context.py

@@ -6,6 +6,7 @@ that later features resolve through owner-qualified selectors.
 
 from __future__ import annotations
 
+import math
 from typing import TYPE_CHECKING, Any
 
 from ..registry import atomic_executor
@@ -61,3 +62,28 @@ def _reference_axis_executor(node: FeaturePlanNode, session: "ExecutionSession",
     # 7. 注册为拓扑上下文，并返回结果对象（携带该轴）。
     session.topology.register_context(node.feature_id, axis)
     return session.result(node, context=axis)
+
+
+@atomic_executor("reference_point")
+def _reference_point_executor(node: FeaturePlanNode, session: "ExecutionSession", sketch: dict[str, Any] | None) -> FeatureResult:
+    """Execute an explicit source-datum point without changing model topology."""
+    del sketch
+    point = node.params.get("point_mm")
+    if (
+        not isinstance(point, list)
+        or len(point) != 3
+        or not all(isinstance(value, (int, float)) and math.isfinite(float(value)) for value in point)
+    ):
+        raise ValueError("reference point requires one finite three-dimensional point")
+    return session.result(node, include_body=False)
+
+
+@atomic_executor("assign_variable")
+def _assign_variable_executor(node: FeaturePlanNode, session: "ExecutionSession", sketch: dict[str, Any] | None) -> FeatureResult:
+    """Replay a source variable declaration after lowering has consumed it."""
+    del sketch
+    name = node.params.get("name")
+    value = node.params.get("value")
+    if not isinstance(name, str) or not name or not isinstance(value, (int, float)) or not math.isfinite(float(value)):
+        raise ValueError("assign_variable requires one finite named value")
+    return session.result(node, include_body=False)