fix: resolve compilation errors by fixing mutable references and removing unused imports

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/modes/diff.rs

@@ -1,6 +1,5 @@
 use anyhow::{anyhow, Result};
 use clap::Command;
-use log::debug;
 use std::io::Read;
 use std::os::fd::FromRawFd;
 use std::str::FromStr;