Merge pull request #733 from AnguseZhang/fix/step_description

refactor: 改用常量STEP_DESCRIPTION增强代码可读性和维护性

Author: Rasic2

agents/matmaster_agent/flow_agents/execution_agent/agent.py

@@ -266,9 +266,9 @@ async def _prepare_retry_fake_success(
         update_plan = copy.deepcopy(ctx.session.state['plan'])
         update_plan['steps'][index]['status'] = PlanStepStatusEnum.PROCESS
         update_plan['steps'][index]['validation_failure_reason'] = validation_reason
-        original_description = ctx.session.state[PLAN]['steps'][index]['description']
+        original_description = ctx.session.state[PLAN]['steps'][index][STEP_DESCRIPTION]
         update_plan['steps'][index][
-            'description'
+            STEP_DESCRIPTION
         ] = f"{original_description}\n\n注意：上次执行因以下原因校验失败，请改进：{validation_reason}"
         yield update_state_event(ctx, state_delta={'plan': update_plan})