Add pre-commit hooks for code quality

- Add .pre-commit-config.yaml with rustfmt, clippy, and cargo check
- Include standard pre-commit hooks for whitespace and file fixes
- Update README with development setup instructions
- Fix formatting and trailing whitespace in various files

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/integration_test.rs

@@ -4,7 +4,6 @@ use predicates::prelude::*;
 use std::env;
 use std::process::Command as StdCommand;
 
-
 #[test]
 fn test_version_command() -> Result<()> {
     let mut cmd = Command::cargo_bin("krust")?;