fix: update CustomSkillsMiddleware.before_agent signature

Add missing 'config' parameter to match new SkillsMiddleware API.

agent/deep_assistant.py

@@ -302,7 +302,7 @@ class CustomSkillsMiddleware(SkillsMiddleware):
         )
         self.project_skills_display = project_skills_display
 
-    def before_agent(self, state, runtime):
+    def before_agent(self, state, runtime, config):
         """Load skills metadata before agent execution.
 
         修改路径显示为相对路径。