fix(chess): reduce top spacer for tighter center positioning

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/js/modules/chess/scenes/game.js

@@ -105,7 +105,7 @@ export function mountGame(el, params) {
         </div>
       </div>
       <!-- Spacer — near center, slightly bottom-biased -->
-      <div style="flex:0.4;"></div>
+      <div style="flex:0.25;"></div>
       <!-- Opponent Bar (compact — keep minimal at top) -->
       <div class="chess-bar" style="display:flex;align-items:center;justify-content:space-between;padding:4px 12px;background:#0f0f1e;">
         <div style="display:flex;align-items:center;gap:8px;">