fix: 按 K-00 约定修复 Python SDK 断线重交与退避

sdk/python/src/nixmsg/__init__.py

@@ -4,7 +4,7 @@ from .async_client import AsyncClient
 from .client import Client
 from .errors import ClosedError, NixMsgError, NotConnectedError
 from .protocol import register_url_from_connect
-from .transport import FakeTransport, PahoTransport
+from .transport import PahoTransport
 from .types import (
     Body,
     ConnectionEvent,
@@ -29,7 +29,6 @@ __all__ = [
     "ClosedError",
     "ConnectionEvent",
     "ConnectionState",
-    "FakeTransport",
     "GroupEvent",
     "IncomingMessage",
     "NixMsgError",