feat: migrate GameRules.gameStatus to GameContext; add false-stalemate test

- gameStatus now accepts GameContext instead of Board so legalMoves
  (which already requires GameContext for castling) is called directly
  without discarding castling rights
- All four existing gameStatus call sites in GameRulesTest migrated to ctx(...)
- New test: castling as sole legal move returns Normal, not Drawn
- GameController.processMove updated to wrap newBoard in GameContext at
  the gameStatus call site (full ctx propagation deferred to Task 6)

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

modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala

@@ -2,7 +2,7 @@ package de.nowchess.chess.controller
 
 import scala.io.StdIn
 import de.nowchess.api.board.{Board, Color, Piece}
-import de.nowchess.chess.logic.{MoveValidator, GameRules, PositionStatus}
+import de.nowchess.chess.logic.{GameContext, MoveValidator, GameRules, PositionStatus}
 import de.nowchess.chess.view.Renderer
 
 // ---------------------------------------------------------------------------
@@ -49,7 +49,7 @@ object GameController:
                   MoveResult.IllegalMove
                 else
                   val (newBoard, captured) = board.withMove(from, to)
-                  GameRules.gameStatus(newBoard, turn.opposite) match
+                  GameRules.gameStatus(GameContext(newBoard), turn.opposite) match
                     case PositionStatus.Normal  => MoveResult.Moved(newBoard, captured, turn.opposite)
                     case PositionStatus.InCheck => MoveResult.MovedInCheck(newBoard, captured, turn.opposite)
                     case PositionStatus.Mated   => MoveResult.Checkmate(turn)

modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala

@@ -38,9 +38,9 @@ object GameRules:
       .toSet
 
   /** Position status for the side whose turn it is (`color`). */
-  def gameStatus(board: Board, color: Color): PositionStatus =
-    val moves   = legalMoves(GameContext(board), color)
-    val inCheck = isInCheck(board, color)
+  def gameStatus(ctx: GameContext, color: Color): PositionStatus =
+    val moves   = legalMoves(ctx, color)
+    val inCheck = isInCheck(ctx.board, color)
     if moves.isEmpty && inCheck then PositionStatus.Mated
     else if moves.isEmpty       then PositionStatus.Drawn
     else if inCheck             then PositionStatus.InCheck

modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala

@@ -62,33 +62,30 @@ class GameRulesTest extends AnyFunSuite with Matchers:
   test("gameStatus: checkmate returns Mated"):
     // White Qh8, Ka6; Black Ka8
     // Qh8 attacks Ka8 along rank 8; all escape squares covered (spec-verified position)
-    val b = board(
+    GameRules.gameStatus(ctx(
       sq(File.H, Rank.R8) -> Piece.WhiteQueen,
       sq(File.A, Rank.R6) -> Piece.WhiteKing,
       sq(File.A, Rank.R8) -> Piece.BlackKing
-    )
-    GameRules.gameStatus(b, Color.Black) shouldBe PositionStatus.Mated
+    ), Color.Black) shouldBe PositionStatus.Mated
 
   test("gameStatus: stalemate returns Drawn"):
     // White Qb6, Kc6; Black Ka8
     // Black king has no legal moves and is not in check (spec-verified position)
-    val b = board(
+    GameRules.gameStatus(ctx(
       sq(File.B, Rank.R6) -> Piece.WhiteQueen,
       sq(File.C, Rank.R6) -> Piece.WhiteKing,
       sq(File.A, Rank.R8) -> Piece.BlackKing
-    )
-    GameRules.gameStatus(b, Color.Black) shouldBe PositionStatus.Drawn
+    ), Color.Black) shouldBe PositionStatus.Drawn
 
   test("gameStatus: king in check with legal escape returns InCheck"):
     // White Ra8 attacks Black Ke8 along rank 8; king can escape to d7, e7, f7
-    val b = board(
+    GameRules.gameStatus(ctx(
       sq(File.A, Rank.R8) -> Piece.WhiteRook,
       sq(File.E, Rank.R8) -> Piece.BlackKing
-    )
-    GameRules.gameStatus(b, Color.Black) shouldBe PositionStatus.InCheck
+    ), Color.Black) shouldBe PositionStatus.InCheck
 
   test("gameStatus: normal starting position returns Normal"):
-    GameRules.gameStatus(Board.initial, Color.White) shouldBe PositionStatus.Normal
+    GameRules.gameStatus(GameContext(Board.initial), Color.White) shouldBe PositionStatus.Normal
 
   test("legalMoves: includes castling destination when available"):
     val c = GameContext(
@@ -114,3 +111,21 @@ class GameRulesTest extends AnyFunSuite with Matchers:
       blackCastling = CastlingRights.None
     )
     GameRules.legalMoves(c, Color.White) should not contain (sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
+
+  test("gameStatus: returns Normal (not Drawn) when castling is the only legal move"):
+    // White King e1, Rook h1 (kingside castling available).
+    // Black Rooks d2 and f2 box the king: d1 attacked by d2, e2 attacked by both,
+    // f1 attacked by f2. King cannot move to any adjacent square without entering
+    // an attacked square or an enemy piece. Only legal move: castle to g1.
+    val c = GameContext(
+      board = board(
+        sq(File.E, Rank.R1) -> Piece.WhiteKing,
+        sq(File.H, Rank.R1) -> Piece.WhiteRook,
+        sq(File.D, Rank.R2) -> Piece.BlackRook,
+        sq(File.F, Rank.R2) -> Piece.BlackRook,
+        sq(File.A, Rank.R8) -> Piece.BlackKing
+      ),
+      whiteCastling = CastlingRights(kingSide = true, queenSide = false),
+      blackCastling = CastlingRights.None
+    )
+    GameRules.gameStatus(c, Color.White) shouldBe PositionStatus.Normal