Add 3D dice roll animation for thrown rocks

Emit the individual rock-die faces (0/0/1/1/2/2) from the battle
resolver so the client can render a real CSS 3D cube per die that
tumbles and settles on the rolled face, replacing the flat random
damage number. Falls back to the flying-rock cue for older battle logs
without per-die data.

internal/game/battle.go

@@ -91,6 +91,9 @@ type BattleEvent struct {
 	// clash: per-seat damage totals / deaths after the exchange.
 	Damage []int  `json:"damage,omitempty"`
 	Died   []bool `json:"died,omitempty"`
+	// rock: individual die faces rolled (each 0, 1, or 2), for the dice
+	// animation; Roll is their sum.
+	Dice []int `json:"dice,omitempty"`
 	// rock: dice total rolled; rock/strip/steal: target pet's fate.
 	Roll        int  `json:"roll"`
 	DamageAfter int  `json:"damageAfter"`
@@ -368,13 +371,15 @@ func (g *Game) resolveBattle() {
 			return false
 		}
 		roll := 0
-		for range dice {
-			roll += g.rollRockDie()
+		faces := make([]int, dice)
+		for i := range dice {
+			faces[i] = g.rollRockDie()
+			roll += faces[i]
 		}
 		dealt, blocked := hitUnit(target, roll)
 		died := !tu.Alive()
 		emit(BattleEvent{
-			Type: "rock", Seat: from, Target: target, Roll: roll,
+			Type: "rock", Seat: from, Target: target, Roll: roll, Dice: faces,
 			DamageAfter: tu.Damage, TargetDied: died,
 		})
 		if blocked {