css subgrid

Shogi.UI/Pages/Play/GameBoard/SeatedGameBoard.razor

@@ -4,7 +4,7 @@
 @using System.Net;
 @inject ShogiApi ShogiApi;
 
-<div style="position: relative;">
+<Stretch style="position: relative;">
 	<GameBoardPresentation Session="Session"
 												 Perspective="Perspective"
 												 OnClickHand="OnClickHand"
@@ -25,7 +25,8 @@
 			</div>
 		</section>
 	}
-</div>
+
+</Stretch>
 
 @code {
 	[Parameter, EditorRequired]