[Rename] Unify Die → Dice naming across the entire project

Standardize all class, interface, file, method, event, field, and variable
names from the inconsistent "Die" form to "Dice", matching the existing
DiceManager/DiceCatalog/DiceCollection convention.

Renamed files (7 + meta): IDie→IDice, DieInstance→DiceInstance,
DieDefinitionSO→DiceDefinitionSO, StandardDieSO→StandardDiceSO,
DieValueCondition→DiceValueCondition, AddPerDieEffect→AddPerDiceEffect,
MultiplyPerDieEffect→MultiplyPerDiceEffect.

Updated all 31 consumer and test files with matching reference changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Assets/Scripts/UI/DicePanelView.cs

@@ -43,7 +43,7 @@ namespace YachtDice.UI
             SetRollButtonState(true, 0, 3);
         }
 
-        public void SetDieValue(int index, int value)
+        public void SetDiceValue(int index, int value)
         {
             if (index >= 0 && index < diceValueTexts.Length)
                 diceValueTexts[index].text = value.ToString();
@@ -55,7 +55,7 @@ namespace YachtDice.UI
                 diceValueTexts[i].text = values[i].ToString();
         }
 
-        public void SetDieLocked(int index, bool isLocked)
+        public void SetDiceLocked(int index, bool isLocked)
         {
             if (index >= 0 && index < diceBackgrounds.Length)
                 diceBackgrounds[index].color = isLocked ? lockedColor : unlockedColor;