fix: resolve private field access and type issues

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

src/services/compression_service.rs

@@ -37,7 +37,7 @@ impl CompressionService {
 
         let reader = engine.open(item_path.clone())
             .map_err(|e| CoreError::Other(anyhow!("Failed to open item file {:?}: {}", item_path, e)))?;
-        Ok(reader)
+        Ok(Box::new(reader))
     }
 }