fix: load designs off-thread and cache recent thumbnails as PNGs

crates/doc/src/tests.rs

@@ -357,3 +357,12 @@ fn input_sketches_lists_every_variant_with_a_sketch_field() {
         );
     }
 }
+
+#[test]
+fn timeline_clones_share_meshes_even_when_cloned_before_tessellation() {
+    let body = solvecraft_kernel::box_solid(Vec3::ZERO, Vec3::new(10., 10., 10.)).unwrap();
+    let a = crate::eval::ModelBody::new("box".into(), body, 1);
+    let b = a.clone();
+    assert!(std::sync::Arc::ptr_eq(&a.mesh(), &b.mesh()));
+    assert!(!a.mesh().triangles.is_empty());
+}