Fix bugs around AI opponents.

internal/ai/shop.go

@@ -7,6 +7,18 @@ import (
 	"github.com/greyson/super-auto-pets-board-game/internal/game"
 )
 
+// deckHasPet reports whether a hypothetical deck still contains at least one
+// pet. A deck of only food (apples) can never field a fighter, so it is an
+// automatic loss — the bot must never voluntarily sell or trade its way there.
+func deckHasPet(deck []game.Card) bool {
+	for _, c := range deck {
+		if c.IsPet() {
+			return true
+		}
+	}
+	return false
+}
+
 // applyTemplateShopEffects mirrors the engine's shop-time triggers on a
 // hypothetical deck: buying an Otter really does come with an apple, and the
 // bot should value that. Only deck-changing effects matter here (coin
@@ -240,6 +252,11 @@ func (b *Bot) decideShop(v *game.View, mem *Memory) *Action {
 			nd = append(nd, cx.simApple())
 			nd = cx.applyTemplateShopEffects(nd, s, game.TriggerSell)
 		}
+		// Never dump the last pet: an all-food deck loses on sight, so this
+		// candidate is off the table no matter how the rollouts score.
+		if !deckHasPet(nd) {
+			continue
+		}
 		cands = append(cands, candidate{
 			act:   &Action{Type: "sell", Cards: ids},
 			decks: [][]game.Card{nd},