refactor(core): integrate Rule module and update GameContext handling

modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala

@@ -10,7 +10,7 @@ import scala.annotation.tailrec
 /** Standard chess rules implementation.
  *  Handles move generation, validation, check/checkmate/stalemate detection.
  */
-object StandardRules extends RuleSet:
+object DefaultRules extends RuleSet:
 
   // ── Direction vectors ──────────────────────────────────────────────
   private val RookDirs: List[(Int, Int)] = List((1, 0), (-1, 0), (0, 1), (0, -1))