fix: Update CustomCodeAgent to properly handle template population using string format

app.py

@@ -241,8 +241,8 @@ class CustomCodeAgent(CodeAgent):
 
     def initialize_system_prompt(self):
         # Override to use tools_dict for template rendering
-        return self.populate_template(
-            self.prompt_templates["system_prompt"],
+        template = self.prompt_templates["system_prompt"]
+        return template.format(
             tools=self.tools_dict,
             task=self.task,
             managed_agents=self.managed_agents,