Close server session after handle stateless request (#1116)

src/mcp/server/streamable_http_manager.py

@@ -190,6 +190,9 @@ class StreamableHTTPSessionManager:
         # Handle the HTTP request and return the response
         await http_transport.handle_request(scope, receive, send)
 
+        # Terminate the transport after the request is handled
+        await http_transport.terminate()
+
     async def _handle_stateful_request(
         self,
         scope: Scope,