[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/Dice/DiceCatalog.cs

@@ -6,11 +6,11 @@ namespace YachtDice.Dice
     [CreateAssetMenu(fileName = "DiceCatalog", menuName = "YachtDice/Dice/Catalog")]
     public class DiceCatalog : ScriptableObject
     {
-        [SerializeField] private List<DieDefinitionSO> dice = new();
+        [SerializeField] private List<DiceDefinitionSO> dice = new();
 
-        public IReadOnlyList<DieDefinitionSO> All => dice;
+        public IReadOnlyList<DiceDefinitionSO> All => dice;
 
-        public DieDefinitionSO FindById(string id)
+        public DiceDefinitionSO FindById(string id)
         {
             for (int i = 0; i < dice.Count; i++)
             {
@@ -21,10 +21,10 @@ namespace YachtDice.Dice
         }
 
 #if UNITY_EDITOR
-        public static DiceCatalog CreateForTest(List<DieDefinitionSO> defs)
+        public static DiceCatalog CreateForTest(List<DiceDefinitionSO> defs)
         {
             var catalog = CreateInstance<DiceCatalog>();
-            catalog.dice = defs ?? new List<DieDefinitionSO>();
+            catalog.dice = defs ?? new List<DiceDefinitionSO>();
             return catalog;
         }
 #endif