Add chess (Oh my gosh big commit)

JoshHeaps.Net/Models/GameState.cs

@@ -0,0 +1,52 @@
+namespace JoshHeaps.Net.Models;
+
+public class GameState
+{
+    public Guid GameId { get; set; }
+
+    // 8x8 board of references. Null if no piece is present.
+    // row 0 at top -> row 7 at bottom (typical 0-based array).
+    public ChessPiece?[,] Board { get; set; }
+
+    // Whose turn is it?
+    public PieceColor CurrentPlayer { get; set; }
+
+    // To detect if en passant is possible, store the position of a pawn that just moved two squares.
+    // If no pawn is currently "en-passant capturable," this could be null.
+    public Position? EnPassantTarget { get; set; }
+
+    // Castling rights: have the rooks or king moved?
+    // In real chess notation, you track it per side, e.g. "KQkq" style. Let’s store boolean flags:
+    public bool WhiteCanCastleKingside { get; set; }
+    public bool WhiteCanCastleQueenside { get; set; }
+    public bool BlackCanCastleKingside { get; set; }
+    public bool BlackCanCastleQueenside { get; set; }
+
+    // Some game status
+    public bool IsCheck { get; set; }
+    public bool IsCheckmate { get; set; }
+    public bool IsStalemate { get; set; }
+
+    // Keep a history of moves if desired
+    public List<string> MoveHistory { get; set; }
+
+    // A list of all pieces to quickly reference them (optional but convenient).
+    // Alternatively, you can iterate the Board array.
+    public List<ChessPiece> Pieces { get; set; }
+
+    public bool WhiteJoined { get; set; } = false;
+    public bool BlackJoined { get; set; } = false;
+    public Guid WhitePlayerId { get; set; }
+    public Guid BlackPlayerId { get; set; }
+
+    // optional: convenience
+    public bool IsOpen => !WhiteJoined || !BlackJoined;
+
+    public GameState()
+    {
+        GameId = Guid.NewGuid();
+        Board = new ChessPiece[8, 8];
+        Pieces = [];
+        MoveHistory = [];
+    }
+}