Make the AI a little smarter.

internal/ai/eval.go

@@ -9,16 +9,34 @@ import (
 )
 
 // winScore converts a simulated battle outcome to a utility for mySeat:
-// win 1, draw 0.5 (nobody gains ground), loss 0.
+// win 1, draw 0.5 (nobody gains ground), loss 0, plus a small margin term.
+//
+// The margin — your surviving pets minus the enemy's — breaks ties among
+// outcomes that share a verdict: a loss where you took most of the enemy down
+// beats a wipe, and a decisive win beats a squeaker. It is capped well under
+// 0.25 so it can never reorder win above draw above loss; it only decides
+// between moves the coarse win/draw/loss signal rates identically. That
+// gradient is what makes the bot play on sensibly when every option looks
+// hopeless — fielding its strongest force instead of picking at random.
 func winScore(res *game.BattleResult, mySeat int) float64 {
+	var base float64
 	switch res.WinnerSeat {
 	case mySeat:
-		return 1
+		base = 1
 	case -1:
-		return 0.5
+		base = 0.5
 	default:
-		return 0
+		base = 0
 	}
+	margin := 0
+	for seat, s := range res.Survivors {
+		if seat == mySeat {
+			margin += s
+		} else {
+			margin -= s
+		}
+	}
+	return base + 0.1*math.Tanh(float64(margin)/3)
 }
 
 // winProb estimates the chance the arranged deck wins the upcoming battle by