Implement thief discard and retain flows

tools/deck/cb/run.mjs

@@ -81,6 +81,7 @@ self.DiscardSelectRemaining = 0
 self.DiscardSelectTotal = 0
 self.DiscardPostShiv = 0
 self.DiscardShivPerPick = 0
+self.RetainSelectActive = false
 self.CombatOver = false
 self.DiscardPile = {}
 self.ExhaustPile = {}