Fix SSE route dependency and align architecture docs

backend/app/services/agent/__init__.py

@@ -1,6 +1,8 @@
-"""Agent服务模块"""
+"""Initialize the app.services.agent package."""
 
 from .qa_agent import QAAgent, ask_compliance_question
 from .session_manager import SessionManager, ChatSession
+# Keep package boundaries explicit so backend imports stay predictable.
+
 
 __all__ = ["QAAgent", "ask_compliance_question", "SessionManager", "ChatSession"]