GUI Pitfall: Close button on search library button

1. Crack a [[Terramorphic Expanse]] or similar.
2. Instead of picking a land from the window that shows you your library, click the red X.
3. ?

After 2. Your only option is to click cancel. There are two problems here:
1. Cancel makes no sense in this case, you cannot undo anything and you must pick a basic land from your library (if there is one).
2. You are no longer able to bring back up library window to pick a card, so you're forced to click cancel.

Start by reproducing the Terramorphic Expanse library-selection flow and inspect the GUI handling for the red X and Cancel actions. Trace how closing the library window changes the available choices; done means the player can recover or exit without being forced into an unusable Cancel-only state.

Written by the indexing model from the issue text.