fix(chess): prevent duplicate players and fix move detection

- Prevent same player from joining as both white and black
- Add validation to reject duplicate players in RoomManager
- Fix spectator status not resetting when joining as player
- Use ref to track latest chess state in ChessBoard for accurate move validation

panel/src/lib/useGameRoom.ts

@@ -56,13 +56,16 @@ export function useGameRoom(roomId: string, userId: string, role?: string) {
                             return {
                                 ...prev,
                                 spectators: [...prev.spectators.filter(s => s.discordId !== msg.player.discordId), msg.player],
-                                isSpectator: isMe ? true : prev.isSpectator,
+                                isSpectator: isMe || prev.isSpectator,
                                 roomStatus: prev.roomStatus === "connecting" ? "waiting" : prev.roomStatus,
                             };
                         }
+                        
+                        const isMe = msg.player.discordId === userId;
                         return {
                             ...prev,
                             players: [...prev.players.filter(p => p.discordId !== msg.player.discordId), msg.player],
+                            isSpectator: isMe ? false : prev.isSpectator,
                             roomStatus: prev.roomStatus === "connecting" ? "waiting" : prev.roomStatus,
                         };
                     });