fix(mcp): prevent internal handler serialization errors from being silently discarded or defaulting to empty strings

server/src/handlers/meta.rs

@@ -276,8 +276,8 @@ impl McpTool for ReadPreferencesHandler {
     async fn execute(&self, _args: Value, state: Arc<MemoryState>) -> Result<String, String> {
         let data = state
             .prefs
-            .read_with(|prefs| serde_json::to_string(prefs).unwrap_or_default());
-        Ok(data)
+            .read_with(|prefs| serde_json::to_string(prefs).map_err(|e| e.to_string()));
+        data
     }
 }