Fix CI workflow: use correct rust-toolchain action (#1)

* Fix CI workflow: use correct rust-toolchain action

* Fix CI: resolve Rust compilation and formatting issues
- Fix rust-toolchain action name in CI workflow
- Add missing Direction import in test modules
- Add missing entry_fees argument to open_position test calls
- Comment out nightly-only rustfmt options
- Auto-format code with cargo fmt

rustfmt.toml

@@ -1,5 +1,6 @@
 edition = "2021"
 max_width = 100
 use_small_heuristics = "Max"
-imports_granularity = "Module"
-group_imports = "StdExternalCrate"
+# Note: imports_granularity and group_imports require nightly Rust
+# imports_granularity = "Module"
+# group_imports = "StdExternalCrate"