test(io): add exportGameContext tests

Add two simple tests for exportGameContext functionality:
1. Test that moves are preserved in PGN output
2. Test that empty game exports headers with proper terminator

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

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

@@ -1,8 +1,9 @@
 package de.nowchess.io.pgn
 
 import de.nowchess.api.board.{PieceType, *}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.api.game.{GameHistory, HistoryMove}
+import de.nowchess.api.move.{PromotionPiece, Move, MoveType}
+import de.nowchess.api.game.{GameHistory, HistoryMove, GameContext}
+import de.nowchess.io.pgn.PgnParser
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -113,3 +114,23 @@ class PgnExporterTest extends AnyFunSuite with Matchers:
     val pgn = PgnExporter.exportGame(Map.empty, history)
     pgn shouldBe "1. e4 *"
 
+  test("exportGameContext: moves are preserved in output") {
+    val moves = List(
+      Move(Square(File.E, Rank.R2), Square(File.E, Rank.R4), MoveType.Normal),
+      Move(Square(File.E, Rank.R7), Square(File.E, Rank.R5), MoveType.Normal)
+    )
+    val ctx = GameContext.initial.copy(moves = moves)
+    val exported = PgnExporter.exportGameContext(ctx)
+
+    exported.contains("e4") shouldBe true
+    exported.contains("e5") shouldBe true
+  }
+
+  test("exportGameContext: empty game returns headers only") {
+    val ctx = GameContext.initial
+    val exported = PgnExporter.exportGameContext(ctx)
+
+    exported.contains("[Event") shouldBe true
+    exported.contains("*") shouldBe true  // Result terminator
+  }
+