flutter: 修改注释和增加一点调试代码

src/ui/flutter/lib/board/pieces_painter.dart

@@ -77,7 +77,7 @@ class PiecesPainter extends PainterBase {
       //
       for (var col = 0; col < 7; col++) {
         //
-        final piece = position.pieceAt(row * 7 + col); // 改为9则全空
+        final piece = position.pieceAt(row * 7 + col); // 初始状态无棋子
 
         if (piece == Piece.noPiece) continue;
 

src/ui/flutter/lib/mill/position.dart

@@ -22,6 +22,11 @@ class Position {
       _board[i] ??= Piece.noPiece;
     }
 
+    // Debugging // 需要一个映射表，从 sq 转换为 board 的坐标！
+    _board[4] = Piece.blackStone;
+    _board[7] = Piece.ban;
+    _board[8] = Piece.whiteStone;
+
     _recorder = MillRecorder(lastCapturedPosition: toFen());
   }