The corporation should not be able to swap regions into servers that already have regions

[NBKelly]

I think we clean it up in the checkpoint if it happens, but it's not even legal to attempt to do this apparently.

https://access.nullsignal.games/CompRules/Null_Signal_Games_Netrunner_Comprehensive_Rules_v24.03.pdf#section*.100

3.6.5.e

In terms of implementation, I think we could have a swap-legal? function in moving which can determine if swaps are legal (for installed cards):

• The region thing should be considered
• Wrong types (ice->not ice) be considered
• two assets in a server
• cards with a server restriction, like ZATO (not install restriction, like off the grid)

(I got confirmation from rules that these are all invalid targets for swaps)