fix: update trait and remove unused io imports

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

src/meta_plugin.rs

@@ -1,5 +1,4 @@
 use anyhow::Result;
-use std::io;
 use rusqlite::Connection;
 use log::debug;
 
@@ -48,7 +47,7 @@ pub trait MetaPlugin {
         false
     }
     
-    fn finalize(&mut self) -> io::Result<String>;
+    fn finalize(&mut self) -> Result<()>;
 
     // Update the meta plugin with new data
     fn update(&mut self, data: &[u8]);