fix(pgn): add SAN disambiguation and check/checkmate suffixes [NCS-42] (#56)

Two bugs in move notation causing PGN import failures in LiChess:

1. Disambiguation: when two pieces of same type can reach same square,
   SAN requires file/rank/full-square prefix (e.g. "Ndf3" not "Nf3").
   Added disambiguate() in PgnExporter and disambiguatePiece() in
   GameEngine, both querying allLegalMoves to find competing pieces.

2. Check/checkmate suffix: "+" and "#" were never appended.
   PgnExporter now threads ctxAfter through moveToAlgebraic and
   calls DefaultRules.isCheck/isCheckmate. GameEngine passes
   PostMoveStatus to translateMoveToNotation for the same result.

Also removes dead notation code in executeMoveBody (result was never
used — not passed to MoveExecutedEvent).

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

---------

Co-authored-by: Janis Eccarius <eccariusjanis@gmail.com>
Reviewed-on: #56

modules/io/src/main/scala/de/nowchess/io/pgn/PgnExporter.scala

@@ -31,7 +31,9 @@ object PgnExporter extends GameContextExport:
       if moves.isEmpty then ""
       else
         val contexts = moves.scanLeft(GameContext.initial)((ctx, move) => DefaultRules.applyMove(ctx)(move))
-        val sanMoves = moves.zip(contexts).map { case (move, ctx) => moveToAlgebraic(move, ctx.board) }
+        val sanMoves = moves.zip(contexts).zip(contexts.tail).map { case ((move, ctxBefore), ctxAfter) =>
+          moveToAlgebraic(move, ctxBefore, ctxAfter)
+        }
 
         val groupedMoves = sanMoves.zipWithIndex.groupBy(_._2 / 2)
         val moveLines = for (moveNumber, movePairs) <- groupedMoves.toList.sortBy(_._1) yield
@@ -48,9 +50,24 @@ object PgnExporter extends GameContextExport:
     else if moveText.isEmpty then headerLines
     else s"$headerLines\n\n$moveText"
 
-  /** Convert a Move to Standard Algebraic Notation using the board state before the move. */
-  private def moveToAlgebraic(move: Move, boardBefore: Board): String =
-    move.moveType match
+  private def disambiguate(from: Square, to: Square, pieceType: PieceType, ctx: GameContext): String =
+    val competitors = DefaultRules
+      .allLegalMoves(ctx)
+      .filter(m => m.to == to && m.from != from && ctx.board.pieceAt(m.from).exists(_.pieceType == pieceType))
+    if competitors.isEmpty then ""
+    else
+      val sameFile = competitors.exists(_.from.file == from.file)
+      val sameRank = competitors.exists(_.from.rank == from.rank)
+      if !sameFile then from.file.toString.toLowerCase
+      else if !sameRank then (from.rank.ordinal + 1).toString
+      else from.toString
+
+  private def moveToAlgebraic(move: Move, ctxBefore: GameContext, ctxAfter: GameContext): String =
+    val suffix =
+      if DefaultRules.isCheckmate(ctxAfter) then "#"
+      else if DefaultRules.isCheck(ctxAfter) then "+"
+      else ""
+    val base = move.moveType match
       case MoveType.CastleKingside  => "O-O"
       case MoveType.CastleQueenside => "O-O-O"
       case MoveType.EnPassant       => s"${move.from.file.toString.toLowerCase}x${move.to}"
@@ -60,18 +77,19 @@ object PgnExporter extends GameContextExport:
           case PromotionPiece.Rook   => "=R"
           case PromotionPiece.Bishop => "=B"
           case PromotionPiece.Knight => "=N"
-        val isCapture = boardBefore.pieceAt(move.to).isDefined
+        val isCapture = ctxBefore.board.pieceAt(move.to).isDefined
         if isCapture then s"${move.from.file.toString.toLowerCase}x${move.to}$promSuffix"
         else s"${move.to}$promSuffix"
       case MoveType.Normal(isCapture) =>
         val dest   = move.to.toString
         val capStr = if isCapture then "x" else ""
-        boardBefore.pieceAt(move.from).map(_.pieceType).getOrElse(PieceType.Pawn) match
+        ctxBefore.board.pieceAt(move.from).map(_.pieceType).getOrElse(PieceType.Pawn) match
           case PieceType.Pawn =>
             if isCapture then s"${move.from.file.toString.toLowerCase}x$dest"
             else dest
-          case PieceType.Knight => s"N$capStr$dest"
-          case PieceType.Bishop => s"B$capStr$dest"
-          case PieceType.Rook   => s"R$capStr$dest"
-          case PieceType.Queen  => s"Q$capStr$dest"
+          case PieceType.Knight => s"N${disambiguate(move.from, move.to, PieceType.Knight, ctxBefore)}$capStr$dest"
+          case PieceType.Bishop => s"B${disambiguate(move.from, move.to, PieceType.Bishop, ctxBefore)}$capStr$dest"
+          case PieceType.Rook   => s"R${disambiguate(move.from, move.to, PieceType.Rook, ctxBefore)}$capStr$dest"
+          case PieceType.Queen  => s"Q${disambiguate(move.from, move.to, PieceType.Queen, ctxBefore)}$capStr$dest"
           case PieceType.King   => s"K$capStr$dest"
+    base + suffix

modules/io/src/test/scala/de/nowchess/io/pgn/PgnExporterTest.scala

@@ -112,3 +112,38 @@ class PgnExporterTest extends AnyFunSuite with Matchers:
     pgn should include("exf8=Q")
     pawnCapturePgn should include("exd3")
     quietPromotionPgn should include("e8=Q")
+
+  test("exportGame disambiguates when two knights can reach same square"):
+    // 1.Nf3 a6 2.d3 a5 3.Nfd2: d3 clears d2 so both Nb1 and Nf3 can reach d2; must emit "Nfd2"
+    val moves = List(
+      Move(sq("g1"), sq("f3")),
+      Move(sq("a7"), sq("a6")),
+      Move(sq("d2"), sq("d3")),
+      Move(sq("a6"), sq("a5")),
+      Move(sq("f3"), sq("d2")),
+    )
+    val pgn = PgnExporter.exportGame(Map.empty, moves)
+    pgn should include("Nfd2")
+
+  test("exportGame appends + after move that gives check"):
+    // 1.e4 e5 2.Qh5 Nc6 3.Qxf7+ — queen captures f7, gives check to black king on e8
+    val moves = List(
+      Move(sq("e2"), sq("e4")),
+      Move(sq("e7"), sq("e5")),
+      Move(sq("d1"), sq("h5")),
+      Move(sq("b8"), sq("c6")),
+      Move(sq("h5"), sq("f7"), MoveType.Normal(isCapture = true)),
+    )
+    val pgn = PgnExporter.exportGame(Map.empty, moves)
+    pgn should include("Qxf7+")
+
+  test("exportGame appends # after checkmate move"):
+    // Fool's mate: 1.f3 e5 2.g4 Qh4#
+    val moves = List(
+      Move(sq("f2"), sq("f3")),
+      Move(sq("e7"), sq("e5")),
+      Move(sq("g2"), sq("g4")),
+      Move(sq("d8"), sq("h4")),
+    )
+    val pgn = PgnExporter.exportGame(Map("Result" -> "*"), moves)
+    pgn should include("Qh4#")