fix: implement PartialEq for OutputFormat and remove unused imports

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

src/modes/common.rs

@@ -10,9 +10,7 @@ use std::collections::HashMap;
 use std::env;
 use std::str::FromStr;
 use strum::IntoEnumIterator;
-use serde::{Deserialize, Serialize};
-
-#[derive(Debug, Clone, strum::EnumString, strum::Display)]
+#[derive(Debug, Clone, strum::EnumString, strum::Display, PartialEq)]
 #[strum(ascii_case_insensitive)]
 pub enum OutputFormat {
     Table,