Fix bugs around AI opponents.

internal/game/battle.go

@@ -1290,11 +1290,14 @@ func (g *Game) runBattle() *BattleResult {
 		}
 	}
 
-	// A single side still holding a pet in play wins; anything else
-	// (everyone out, or a stalemate with pets on both sides) is a draw.
+	// A single side that can still field a pet wins; anything else (everyone
+	// out, or a stalemate with pets on both sides) is a draw. We test canField,
+	// not unit, because the loop can break the instant one side runs out while
+	// the other's current pet has just fainted — that side still has pets left
+	// in its stack (it simply wasn't refilled) and is the rightful winner.
 	winner := -1
 	for seat, s := range sides {
-		if s.unit != nil {
+		if s.canField() {
 			if winner >= 0 {
 				winner = -1 // stalemate / >2-player safety
 				break

internal/game/golden45_test.go

@@ -156,6 +156,23 @@ func TestManateeSelfRockFatalStillAddsApples(t *testing.T) {
 	}
 }
 
+// A player whose only in-play pet faints to its own play effect (Manatee's
+// self-rock) still wins if it has pets left in its deck and the opponent has
+// none. The battle loop breaks the instant the opponent runs out — before the
+// survivor's next pet is revealed — so the winner must be decided by who can
+// still field a pet, not by who happens to have one in play at that instant.
+func TestSelfFaintWithReserveStillWins(t *testing.T) {
+	g, _, _ := testGame(t)
+	g.RollDie = func() int { return 2 } // 2 rocks = 4 damage, fatal to the 3-power Manatee
+	res := forceBattle(t, g,
+		[]Card{g.goldenPet(t, "Manatee"), g.pet("Reserve", 5)},
+		[]Card{g.newApple()}, // opponent has only food — no pet, ever
+	)
+	if res.WinnerSeat != 0 {
+		t.Fatalf("seat 0 should win with a reserve pet vs an all-food deck, got winner %d", res.WinnerSeat)
+	}
+}
+
 // Poison Dart Frog, once set aside, throws rocks each time a Bee is played.
 func TestPoisonDartFrogBeeRocks(t *testing.T) {
 	g, _, _ := testGame(t)