Bug: disconnect handler always sets winner to undefined in simultaneous-disconnect path

[dennisthemenacing]

Bug

In src/sockets/chessSockets.ts, the disconnect event handler has a logic error that causes the game outcome to always have winner: undefined when both players are offline.

Root Cause

The sequence is:

const game = gameManager.disconnect(userId); // marks current player as connected: false

if (!game.players.white?.connected && !game.players.black?.connected) {
  game.outcome = {
    // Both are already false at this point — ternary always returns undefined
    winner: game.players.white?.connected ? 'white' : game.players.black?.connected ? 'black' : undefined,
    reason: 'resignation',
  };
}

After gameManager.disconnect(userId) runs, the disconnecting player is already marked connected: false. So when the both-offline check passes, both game.players.white?.connected and game.players.black?.connected are false. The winner ternary therefore always resolves to undefined.

Impact

When a player disconnects while their opponent is already disconnected (e.g. opponent dropped then this player drops before the 5-second timer fires), the game is erased with outcome = { winner: undefined, reason: 'resignation' }. No player is credited a win.

Expected Behavior

The winner should be the player who was still connected before this disconnect — i.e., the opponent of userId.

Suggested Fix

Capture the still-connected color before calling gameManager.disconnect, or derive the winner from userId directly:

const playerColor = /* derive from game before disconnect */;
const game = gameManager.disconnect(userId);
if (!game.players.white?.connected && !game.players.black?.connected) {
  const winnerColor = playerColor === 'white' ? 'black' : 'white';
  game.outcome = {
    winner: game.players[winnerColor] ? winnerColor : undefined,
    reason: 'resignation',
  };
}

Related

The existing getPlayerColor private method on GameManager could expose this info, but it's currently private. Alternatively, the socket layer could determine the disconnecting player's color before calling disconnect.