refactor: remove connection storage from plugin structs and pass as argument

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

src/meta_plugin.rs

@@ -60,10 +60,10 @@ pub trait MetaPlugin {
         false
     }
     
-    fn finalize(&mut self) -> Result<()>;
+    fn finalize(&mut self, conn: &Connection) -> Result<()>;
 
     // Update the meta plugin with new data
-    fn update(&mut self, data: &[u8]);
+    fn update(&mut self, data: &[u8], conn: &Connection);
 
     fn meta_name(&mut self) -> String;