refactor: remove unused code and fields

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

src/modes/common.rs

@@ -106,9 +106,6 @@ pub fn get_format_box_chars_no_border_line_separator() -> TableFormat {
         .build()
 }
 
-pub fn get_digest_type_meta(digest_type: MetaPluginType) -> String {
-    format!("digest_{}", digest_type.to_string().to_lowercase())
-}