chore: fix all compiler warnings

- cmd_result.rs: remove unused Point3 and Rad imports (SWEEP block)
- scene/mod.rs: remove unused Solid3D struct import
- commands.rs: drop unnecessary `mut` on new_entities (REFCLOSE block)
- refedit.rs: annotate insert_handle with #[allow(dead_code)]

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/scene/mod.rs

@@ -35,7 +35,7 @@ pub use wire_model::WireModel;
 
 use crate::command::EntityTransform;
 use acadrust::entities::{BoundaryEdge, BoundaryPath, Hatch as DxfHatch, PolylineEdge, Solid as DxfSolid};
-use acadrust::entities::{Block, BlockEnd, Insert as DxfInsert, Solid3D};
+use acadrust::entities::{Block, BlockEnd, Insert as DxfInsert};
 use acadrust::objects::ObjectType;
 use acadrust::types::Vector2;
 use acadrust::{CadDocument, EntityType, Handle, TableEntry};