feat: initial project structure with Snake.Core, CLI and Avalonia skeleton

Snake.Core/Board.cs

@@ -0,0 +1,24 @@
+namespace Snake.Core;
+
+public sealed class Board
+{
+    public Board(int width, int height)
+    {
+        if (width < 2)
+            throw new ArgumentOutOfRangeException(nameof(width), "Width must be at least 2.");
+
+        if (height < 2)
+            throw new ArgumentOutOfRangeException(nameof(height), "Height must be at least 2.");
+
+        Width = width;
+        Height = height;
+    }
+
+    public int Width { get; }
+
+    public int Height { get; }
+
+    public bool IsWithinBounds(Position position) =>
+        position.X >= 0 && position.X < Width &&
+        position.Y >= 0 && position.Y < Height;
+}