feat: update workspace paths and enhance gitignore

- Updated stablediffusion crate path from "../stable-diffusion-burn" to "./crates/stable-diffusion-burn" for proper workspace resolution
- Enhanced .gitignore to include generated model files (.mpk, .pt, .bin, .safetensors, .ckpt) and user_data directory
- Added Cargo.lock to gitignore with appropriate comment
- Reorganized IDE files section in gitignore for better clarity
- Added newline at end of file for proper formatting

crates/stable-diffusion-burn/burn-crates/burn-backend-tests/tests/cubecl/cat.rs

@@ -0,0 +1,42 @@
+use super::*;
+use burn_tensor::Tolerance;
+use burn_tensor::{Distribution, Tensor, backend::Backend};
+
+#[test]
+fn cat_should_match_reference_backend_dim0() {
+    test_same_as_reference([6, 256], 2, 0);
+}
+
+#[test]
+fn cat_should_match_reference_backend_dim1() {
+    test_same_as_reference([6, 256], 2, 1);
+}
+
+#[test]
+fn cat_should_support_uneven_launch() {
+    test_same_as_reference([1, 137], 2, 0);
+}
+
+fn test_same_as_reference(shape: [usize; 2], num_tensors: usize, dim: usize) {
+    let device = Default::default();
+    TestBackend::seed(&device, 0);
+
+    let tensors = (0..num_tensors)
+        .map(|_| {
+            Tensor::<TestBackend, 2>::random(shape, Distribution::Default, &Default::default())
+        })
+        .collect::<Vec<_>>();
+    let tensors_ref = tensors
+        .iter()
+        .map(|tensor| {
+            Tensor::<ReferenceBackend, 2>::from_data(tensor.to_data(), &Default::default())
+        })
+        .collect::<Vec<_>>();
+
+    let tensor = Tensor::<TestBackend, 2>::cat(tensors, dim);
+    let tensor_ref = Tensor::<ReferenceBackend, 2>::cat(tensors_ref, dim);
+
+    tensor
+        .into_data()
+        .assert_approx_eq::<FloatElem>(&tensor_ref.into_data(), Tolerance::default());
+}