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/fusion.rs

@@ -0,0 +1,41 @@
+//! Burn tensor and autodiff tests for CubeCL backends with fusion enabled.
+
+#![allow(
+    clippy::single_range_in_vec_init,
+    clippy::duplicate_mod,
+    reason = "false positive"
+)]
+extern crate alloc;
+
+#[cfg(feature = "cube")]
+#[path = "."]
+mod fusion {
+    pub type FloatElemType = f32;
+    pub type IntElemType = i32;
+
+    #[path = "common/backend.rs"]
+    mod backend;
+    pub use backend::prelude::*;
+
+    // NOTE:
+    // We re-include the tensor and autodiff test suites after overriding `TestBackend`
+    // with `Fusion<TestBackend>`. This intentionally duplicates module names and test
+    // logic to execute the same tests under fusion.
+    pub type TestBackend = burn_fusion::Fusion<backend::TestBackend>;
+    pub type TestTensor<const D: usize> = Tensor<TestBackend, D>;
+    pub type TestTensorInt<const D: usize> = Tensor<TestBackend, D, burn_tensor::Int>;
+    pub type TestTensorBool<const D: usize> = Tensor<TestBackend, D, burn_tensor::Bool>;
+
+    // Tensor tests
+    mod tensor {
+        include!("common/tensor.rs");
+    }
+
+    // Autodiff tests
+    mod autodiff {
+        include!("common/autodiff.rs");
+    }
+
+    // Fusion tests
+    include!("fused_ops/mod.rs");
+}