style: apply cargo fmt across entire Rust codebase

- Remove Rust formatting check from CI workflow since formatting is now applied
- Standardize import ordering and organization throughout codebase
- Fix indentation, spacing, and line breaks for consistency
- Clean up trailing whitespace and formatting inconsistencies
- Apply rustfmt to all Rust source files including checkpoint, sandbox, commands, and test modules

This establishes a consistent code style baseline for the project.

src-tauri/tests/sandbox/common/mod.rs

@@ -1,8 +1,8 @@
 //! Common test utilities and helpers for sandbox testing
+pub mod claude_real;
 pub mod fixtures;
 pub mod helpers;
-pub mod claude_real;
 
+pub use claude_real::*;
 pub use fixtures::*;
 pub use helpers::*;
-pub use claude_real::*;