That's a good point - thanks for the feedback! Going infinite really wasn't intended, and that does seem way too easy particularly in the earlier scenarios. I thought I had a cheeky little block for this that prevented you from shuffling your discard back into your deck twice during a turn, but apparently I never implemented it.
I just updated the game so that cards you play for an action only go into the discard pile once you're out of actions. I weighed some other options, but this seems like the cleanest. You can still engineer your deck to have some explosive turns, but I think the decisions to do that are more interesting.