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/user.rs

@@ -58,7 +58,7 @@ impl MetaPlugin for UserMetaPlugin {
         for (name, value) in values {
             if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
                 name, 
-                value, 
+                serde_yaml::Value::String(value), 
                 self.base.outputs()
             ) {
                 metadata.push(meta_data);