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/e2e/mod.rs

@@ -2,4 +2,4 @@
 #[cfg(test)]
 mod agent_sandbox;
 #[cfg(test)]
-mod claude_sandbox; 
+mod claude_sandbox;