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/underframe.js

@@ -91,13 +91,13 @@ export function Underframe({ view, uid = null, row, col, actions, name = '', bus
       <path class="uframe__corner" d="M-100 0 L-86 -14 M-100 0 L-86 14 M100 0 L86 -14 M100 0 L86 14 M0 -100 L-14 -86 M0 -100 L14 -86 M0 100 L-14 86 M0 100 L14 86" />
     </svg>
     ${actions.retreat ? html`<button type="button" class="uframe__btn uframe__btn--retreat" disabled=${busy} onPointerDown=${stop}
-        onClick=${(e) => { stop(e); onRetreat?.(); }} title="撤退至整备区" aria-label="撤退">
-      <${RetreatGlyph} /><span class="uframe__label">撤退</span>
+        onClick=${(e) => { stop(e); onRetreat?.(); }} title=${actions.sell != null ? '撤退至整备区（Q）' : '撤退至整备区'} aria-label="撤退" aria-keyshortcuts=${actions.sell != null ? 'Q' : undefined}>
+      <${RetreatGlyph} /><span class="uframe__label">${actions.sell != null ? '撤退[Q]' : '撤退'}</span>
     </button>` : null}
     ${actions.sell != null ? html`<button type="button" class="uframe__btn uframe__btn--sell" disabled=${busy} onPointerDown=${stop}
-        onClick=${(e) => { stop(e); onSell?.(); }} title=${`出售（+${actions.sell} 资金）`} aria-label=${`出售，获得 ${actions.sell} 资金`}>
+        onClick=${(e) => { stop(e); onSell?.(); }} title=${`出售（+${actions.sell} 资金，X）`} aria-label=${`出售，获得 ${actions.sell} 资金`} aria-keyshortcuts="X">
       <${PlateIcon} sprite="icon_sell" glyph="sell" tone="sell" />
-      <span class="uframe__label">出售</span>
+      <span class="uframe__label">出售[X]</span>
       <${HexBadge} value=${`+${actions.sell}`} tone="gold" size="sm" class="uframe__price" />
     </button>` : null}
     ${actions.destroy ? html`<button type="button" class=${cx('uframe__btn', 'uframe__btn--destroy')} disabled=${busy} onPointerDown=${stop}