Export the current 3D view as 2D DXF with optional hidden lines (#1449)

Adds File > Export > Current View as DXF: the visible bodies projected from the current camera onto 2D LINE/LWPOLYLINE entities, with hidden edges omitted or dashed.

Co-authored-by: cronos <19868002+crono2250@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/engine/src/tests/path_scope.rs

@@ -29,6 +29,7 @@ fn file_commands_stay_inside_the_agents_folders() {
             ("file.save_as", json!({"path": at(&out, "x.solidcraft")})),
             ("file.save", json!({"path": at(&root, "../out/x.solidcraft")})),
             ("file.export", json!({"path": at(&out, "x.stl")})),
+            ("file.export_view_dxf", json!({"path": at(&out, "x.dxf"),"camera":render::Camera::default()})),
             ("file.export", json!({"path": at(&out, "x.json"), "format": "json"})),
             ("file.save_as", json!({"path": at(&out, "x.json"), "format": "json", "preview": true})),
             ("parameters.export", json!({"path": at(&out, "x.csv")})),