Import glTF 2.0 files (.glb, .gltf) as mesh bodies (#1512)

glTF files open, insert and drop like 3MF/STL/OBJ: a component named after the file, the node tree as nested rigid components, repeated meshes as occurrences, metres to mm, Y up turned to Z up by default (up: z keeps axes), materials as PBR appearances. Bounded, hostile-input tested reader; no new persisted data. Closes #1505.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/lib.rs

@@ -953,7 +953,7 @@ impl SolveApp {
         file_load::begin(self, path, true);
     }
 
-    /// Insert a STEP file's bodies (an Import base feature) or a 3MF/STL file's meshes into the
+    /// Insert a STEP file's bodies (an Import base feature) or a mesh file's meshes into the
     /// current design.
     pub fn insert_path(&mut self, path: &str) {
         let cmd = if solidcraft_engine::io::is_mesh_path(path) { "file.insert_mesh" } else { "file.insert_step" };
@@ -967,7 +967,7 @@ impl SolveApp {
         }
     }
 
-    /// A dropped file: a STEP, 3MF or STL file joins a design that has features, anything else
+    /// A dropped file: a STEP or mesh file (3MF, STL, OBJ, glTF) joins a design that has features, anything else
     /// opens.
     pub fn drop_path(&mut self, path: &str) {
         let import = solidcraft_engine::io::is_step_path(path) || solidcraft_engine::io::is_mesh_path(path);