fix: wrap string values in Value::String for process_metadata_outputs

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

src/meta_plugin/magic.rs

@@ -107,7 +107,7 @@ impl MagicFileMetaPlugin {
                     // Use process_metadata_outputs to handle output mapping
                     if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
                         name, 
-                        result, 
+                        serde_yaml::Value::String(result), 
                         self.base.outputs()
                     ) {
                         metadata.push(meta_data);