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-collective/multinode-tests/README.md

@@ -0,0 +1,32 @@
+# Integration test for burn collective operations with multiple nodes and devices.
+
+Run `cargo run --bin test_launcher`
+
+There are 3 binaries:
+
+## node.rs
+
+Launches `n` threads each simulating a different device. Currently the backend is NdArray,
+so everything is CPU. The program takes a file with configurations and input data.
+
+## global.rs
+
+Runs the global orchestrator, who is responsible for responding to global collective operation
+requests. In the case of an all-reduce, the orchestrator responds with a strategy for reducing,
+and the node can do the reduction independently.
+
+## test_launcher.rs
+
+Generates input data, calculates the expected results, and launches the nodes each with their
+own inputs in a separate file.
+
+The topology is [4, 4, 4, 4]. This means 4 nodes are launched,
+each with 4 threads (for each device).
+
+The global orchestrator (`global.rs`) is also launched.
+
+## Output
+
+The outputs and inputs for each node and the orchestrator are written to the `target/test_files` folder
+
+If the nodes or orchestrator stall, there is a timeout.