add model settings for a more stable pr_summary_agent

Author: xueyulinn

codehawk/agents/pr_summary_agent.py

@@ -1,6 +1,6 @@
 import json
 
-from agents import Agent, Runner, trace
+from agents import Agent, Runner, trace, ModelSettings
 
 from codehawk.agents.prompts import PR_SUMMARY_SYSTEM_PROMPT
 from codehawk.github.dto.pull_request_dto import (
@@ -13,6 +13,7 @@
     name="Github Pull Request Summary Agent",
     instructions=PR_SUMMARY_SYSTEM_PROMPT,
     model="gpt-5.5",
+    model_settings=ModelSettings(temperature=0.2, top_p=0.9)
 )