Fix OMNISTONE... longer windows, less RNG

Omnistone needs to be improved to deliver the dream. The usage windows need to be longer, and there needs to be some control given to the player.

Here is a brainstorm idea..

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Give the player an "omnistone keystone selector deck GUI" a bit like kindred mark target.

Draw 3 random keystones into the deck at game start, with one "discard token". They can discard a single card, or the entire deck (but not the active keystone, if one is active).

Let the player pick the active keystone, and lock it in for 5 minutes.

After 5 minutes, they can (but are not required to) switch to another keystone in their deck (and the old one stays in their deck)

Every 5 minutes give the player another "discard token".

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Discuss...