fix: remove unused imports and update method signatures

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/meta_plugin.rs

@@ -1,6 +1,7 @@
 use anyhow::Result;
 use log::debug;
 use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
 
 pub mod program;
 pub mod digest;