fix(rectification): show choice-card prompt instead of hiding it

BUG-401 hid the legend to avoid duplicating Agent copy. After the
question contract, the Agent only leads in, so the persisted stem
must be visible on the card.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/rectification-choice-card.tsx

@@ -42,7 +42,7 @@ export function RectificationChoiceCard(props: RectificationChoiceCardProps) {
       aria-label={props.card.scoring ? "校正判断" : "盘外核对"}
     >
       <fieldset className="birth-time-choice-question" disabled={props.pending || props.disabled || Boolean(selectedKey)}>
-        <legend className="sr-only">{props.card.prompt}</legend>
+        <legend>{props.card.prompt}</legend>
         {props.card.why ? <p className="rectification-choice-why">{props.card.why}</p> : null}
         <div className="birth-time-primary-choices">
           {primary.map((option, index) => (