test: add test coverage for a01 mqtt client

[allenporter]

Add tests for the a01 mqtt client. This tests an arbitrary command just to have end to end request parsing in place. This brings the entire project up to to 83% test coverage.

---------- coverage: platform darwin, python 3.13.0-final-0 ----------
Name                                                    Stmts   Miss  Cover   Missing
-------------------------------------------------------------------------------------
...
roborock/version_a01_apis/__init__.py                       2      0   100%
roborock/version_a01_apis/roborock_client_a01.py           52      6    88%   126-128, 135-136, 141
roborock/version_a01_apis/roborock_mqtt_client_a01.py      46      1    98%   35
...
-------------------------------------------------------------------------------------
TOTAL                                                    3353    578    83%