Fix: hydrate session state in create_session for VertexAiSessionService

Author: AbhishekMauryaGEEK

src/google/adk/sessions/vertex_ai_session_service.py

@@ -138,6 +138,16 @@ async def create_session(
       logger.debug('Create session response: %s', api_response)
       get_session_response = api_response.response
       session_id = get_session_response.name.split('/')[-1]
+    try:
+      hydrated_session = await self.get_session(
+        app_name=app_name,
+        user_id=user_id,
+        session_id=session_id,
+      )
+      if hydrated_session is not None:
+        return hydrated_session
+    except Exception:
+      logger.debug("Hydration via get_session failed, falling back")
 
     session = Session(
         app_name=app_name,