Q / X hotkeys retreat and sell the selected operator in prep (#114)

Q retreats and X sells the selected operator during prep, through the same buttons (never an item, never while typing in a field); the buttons show [Q] / [X]. Contributed by @SpiritedAwayCN.

public/js/ui/settings.js

@@ -73,7 +73,7 @@ export function SettingsModal({ open, onClose }) {
       </div>
       ${touchUi
         ? html`<p class="set-hint">触屏操作：点击单位选中（撤退 / 出售）· 长按单位或卡牌查看详情 · 拖动部署后滑动选择朝向</p>`
-        : html`<p class="set-hint">快捷键：<kbd>R</kbd> 刷新 · <kbd>F</kbd> 冻结 · <kbd>D</kbd> 升级 · <kbd>Space</kbd> 准备就绪 · <kbd>Esc</kbd> 关闭弹窗 · 右键查看详情</p>`}
+        : html`<p class="set-hint">快捷键：<kbd>R</kbd> 刷新 · <kbd>F</kbd> 冻结 · <kbd>D</kbd> 升级 · <kbd>Q</kbd> 撤退选中干员 · <kbd>X</kbd> 出售选中干员 · <kbd>Space</kbd> 准备就绪 · <kbd>Esc</kbd> 关闭弹窗 · 右键查看详情</p>`}
     </div>
   <//>`;
 }