screen reader and keyboard usability pass

frontend/src/App.tsx

@@ -4,6 +4,7 @@ import { motion, AnimatePresence, MotionConfig } from 'motion/react'
 import { IconShare2 } from '@tabler/icons-react'
 import Grid from './components/Grid'
 import CluePanel from './components/CluePanel'
+import ClueNav from './components/ClueNav'
 import ActiveClue from './components/ActiveClue'
 import Header from './components/Header'
 import InfoBar from './components/InfoBar'
@@ -309,6 +310,7 @@ export default function App() {
             <div className="grid-column">
               <h2 className="visually-hidden">{t('app.crosswordGrid')}</h2>
               <Grid />
+              <ClueNav />
               <div className="game-input-mode" role="group" aria-label={t('settings.display.inputMode')}>
                 {(['auto', 'keyboard', 'stylus'] as const).map(m => (
                   <button key={m} type="button"