fix: update process_metadata_outputs to handle serde_yaml::Value

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

src/meta_plugin/digest.rs

@@ -169,7 +169,7 @@ impl MetaPlugin for DigestMetaPlugin {
             // Add the selected hash output
             if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
                 output_name, 
-                hash_value, 
+                serde_yaml::Value::String(hash_value), 
                 &self.outputs
             ) {
                 metadata.push(meta_data);