[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/Scoring/ScoreResult.cs

@@ -17,7 +17,7 @@ namespace YachtDice.Scoring
 
         public int FinalScore => Mathf.FloorToInt((BaseScore + FlatBonus) * Multiplier);
 
-        public static ScoreResult Create(int baseScore, IReadOnlyList<IDie> dice, CategoryDefinition category)
+        public static ScoreResult Create(int baseScore, IReadOnlyList<IDice> dice, CategoryDefinition category)
         {
             return new ScoreResult
             {