fix: remove unused imports and make unused fields private

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

src/args.rs

@@ -1,5 +1,4 @@
 use std::path::PathBuf;
-use std::str::FromStr;
 
 use clap::*;
 use anyhow::{Error, anyhow};
@@ -174,8 +173,8 @@ impl FromStr for NumberOrString {
  */
 #[derive(Debug, Clone)]
 pub struct KeyValue {
-    pub key: String,
-    pub value: String,
+    pub(crate) key: String,
+    pub(crate) value: String,
 }
 
 impl FromStr for KeyValue {