Guardian Beast control loss handling

ugh yea, notably it is already asymmetrical:
if I steal something with one of the real Layer 2 implementations, e.g. `Confiscate` and then destroy the aura it will currently move back to the previous controller :/

I think the Map entry probably always needs to be removed when the duration ends, so maybe the check belongs inside `controllerChangeZoneCorrection` instead...?
However this means `getController()` would have to return the zone owner where the card currently sits (if there is one).

Either way seems complicated enough that I'd also like a clear judge answer first, but since this PR only helps to clean up the hidden KW I'll just merge for now until an eventual revisit

_Originally posted by @tool4ever in https://github.com/Card-Forge/forge/issues/11805#issuecomment-5582429316_