修改了nanobot，往Hermes agent的风格走，进度1/3

app-instance/backend/beaver/engine/session/__init__.py

@@ -0,0 +1,15 @@
+"""Session state and persistence."""
+
+from .manager import SessionManager
+from .models import MessageRecord, SessionRecord, SessionUsage
+from .search import SessionSearchService
+from .store import SessionStore
+
+__all__ = [
+    "MessageRecord",
+    "SessionManager",
+    "SessionRecord",
+    "SessionSearchService",
+    "SessionStore",
+    "SessionUsage",
+]