Coming to work here is a ‘reasonable excuse’ for entering Wales. If you are lodging here then my understanding is that you are effectively a ‘local’ and can undertake any activity in line with current regulations and guidance.
That’s certainly my understanding. Well, being Pedantic, it’s a reasonable excuse for someone in England to travel anywhere. Our rules stop us entering England during their lockdown, England’s lockdown rules stop them travelling at all. Coz Boris didn’t want to be seen to legitimise any devolved Nation’s lockdown, until he decided England needed one.