feat(cadfs): expand selector provenance coverage

cadfs_to_cdsl/selector_binding.py

@@ -123,7 +123,10 @@ def _selector_roots(feature: dict[str, Any]) -> list[dict[str, Any]]:
     for name in ("end_condition", "reverse_end_condition"):
         condition = (feature.get("params") or {}).get(name)
         reference = condition.get("reference") if isinstance(condition, dict) else None
-        if isinstance(reference, dict):
+        # A source-sketch vertex is an immutable extent datum, not a topology
+        # selector.  It has no runtime record to bind; the extent executor
+        # consumes its validated point directly.
+        if isinstance(reference, dict) and reference.get("kind") != "source_vertex":
             roots.append(reference)
     return roots