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 <noreply@anthropic.com>

src/modules/home/modify/refedit.rs

@@ -23,7 +23,8 @@ use crate::command::{CadCommand, CmdResult};
 /// Active REFEDIT session.  Lives in `DocumentTab::refedit_session`.
 #[derive(Debug, Clone)]
 pub struct RefEditSession {
-    /// The INSERT entity being edited.
+    /// The INSERT entity being edited (kept for future REFCLOSE DISCARD).
+    #[allow(dead_code)]
     pub insert_handle: Handle,
     /// Name of the block being edited.
     pub block_name: String,