Improve AI to stop selling everything.

internal/ai/shop.go

@@ -242,11 +242,27 @@ func (b *Bot) decideShop(v *game.View, mem *Memory) *Action {
 		}
 		return 0
 	})
+	// Selling a pet permanently trades a body for a temporary apple — the
+	// apple's one-battle buff shows up in the rollout, but it vanishes next
+	// round, so the persistent value of the pet is simply destroyed. The
+	// future-value term barely registers this (normFuture squashes small deck
+	// swings), which once let the bot treat "sell my worst pet" as free and
+	// bleed its board down to a single pet over successive shop turns. This
+	// explicit penalty prices the loss back in: it scales with the persistent
+	// worth of the pets sold and with how much the future still matters
+	// (1-alpha), so it bites hardest early and fades to nothing in the final
+	// round, where selling for a decisive last battle is a legitimate play the
+	// rollout can judge on its own.
+	futureWeight := 1 - immediateWeight(v)
 	for k := 1; k <= min(3, len(sellable)); k++ {
 		ids := make([]string, 0, k)
 		nd := slices.Clone(deck)
+		petValueSold := 0.0
 		for _, s := range sellable[:k] {
 			ids = append(ids, s.ID)
+			if s.IsPet() {
+				petValueSold += keepValue(s)
+			}
 			idx := slices.IndexFunc(nd, func(c game.Card) bool { return c.ID == s.ID })
 			nd = slices.Delete(nd, idx, idx+1)
 			nd = append(nd, cx.simApple())
@@ -260,6 +276,7 @@ func (b *Bot) decideShop(v *game.View, mem *Memory) *Action {
 		cands = append(cands, candidate{
 			act:   &Action{Type: "sell", Cards: ids},
 			decks: [][]game.Card{nd},
+			bias:  -sellPetPenalty * futureWeight * petValueSold,
 		})
 	}
 
@@ -297,6 +314,13 @@ func (b *Bot) decideShop(v *game.View, mem *Memory) *Action {
 				base = slices.Delete(base, idx, idx+1)
 				base = cx.applyTemplateShopEffects(base, t, game.TriggerTriple)
 			}
+			// Never bet the whole board on the trade: the reward is the top of
+			// the next tier's deck, which can be a food card (or nothing, if the
+			// deck is spent), so trading away the last pets risks an all-food,
+			// auto-losing deck. Mirror the sell guard and skip such a trade.
+			if !deckHasPet(base) {
+				continue
+			}
 			pool := cx.unseenPool(v.Round + 1)
 			if len(pool) == 0 {
 				pool = game.TierContentsForPack(v.Pack, v.Round+1)