Quiz UX: remove popups, hide skipped questions warning

- safeNavigate: removed window.confirm() entirely — navigating between
  question numbers never loses answers (they're in React state), so the
  popup was wrong and annoying
- handleSubmit: replaced window.confirm() with a 3s toast pill at the
  bottom of the screen (dark, slides up, fades away automatically)
- ModeSelectScreen: removed skipped-questions warning block — internal
  extraction detail, not useful to show users
- Added fadeInUp CSS keyframe for the toast animation

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

frontend/src/index.css

@@ -265,6 +265,11 @@ body {
 .spinner { display: inline-block; width: 20px; height: 20px; border: 3px solid var(--border); border-top-color: var(--primary); border-radius: 50%; animation: spin 0.6s linear infinite; }
 @keyframes spin { to { transform: rotate(360deg); } }
 
+@keyframes fadeInUp {
+  from { opacity: 0; transform: translateX(-50%) translateY(8px); }
+  to   { opacity: 1; transform: translateX(-50%) translateY(0); }
+}
+
 /* ── Section items ──────────────────────────────────────────── */
 .section-item { display: flex; justify-content: space-between; align-items: center; padding: 12px 16px; border: 1px solid var(--border); border-radius: 8px; margin-bottom: 8px; background: var(--card-bg); }
 

frontend/src/pages/QuizPage.jsx

@@ -85,18 +85,6 @@ function ModeSelectScreen({ quiz, voices, onStart }) {
           {quiz.time_limit_minutes ? ` · ${quiz.time_limit_minutes} min limit` : ''}
         </p>
 
-        {skipped.length > 0 && (
-          <div style={{ background: '#fffbeb', border: '1px solid #fcd34d', borderRadius: 8, padding: 12, marginBottom: 20, textAlign: 'left' }}>
-            <p style={{ margin: '0 0 6px', fontWeight: 600, fontSize: '0.85rem', color: '#92400e' }}>
-              ⚠️ {skipped.length} question{skipped.length > 1 ? 's' : ''} skipped (no correct answer found):
-            </p>
-            <ul style={{ margin: 0, paddingLeft: 16 }}>
-              {skipped.map((q, i) => (
-                <li key={i} style={{ fontSize: '0.8rem', color: '#78350f', marginBottom: 2 }}>{q}…</li>
-              ))}
-            </ul>
-          </div>
-        )}
 
         <p style={{ fontWeight: 600, marginBottom: 16, color: '#374151' }}>Choose how to take this quiz:</p>
         <div style={{ display: 'flex', gap: 12, justifyContent: 'center', marginBottom: 20 }}>
@@ -147,9 +135,17 @@ export default function QuizPage() {
   const [attemptId, setAttemptId] = useState(null)
   const [timeLeft, setTimeLeft] = useState(null)
   const [totalTime, setTotalTime] = useState(null)
+  const [toast, setToast] = useState('')
   const timerRef = useRef(null)
+  const toastRef = useRef(null)
   const hasStarted = useRef(false)
 
+  const showToast = (msg) => {
+    setToast(msg)
+    clearTimeout(toastRef.current)
+    toastRef.current = setTimeout(() => setToast(''), 3000)
+  }
+
   useEffect(() => {
     const load = async () => {
       try {
@@ -198,21 +194,13 @@ useEffect(() => {
 
   const setAnswer = (questionId, value) => setAnswers(prev => ({ ...prev, [questionId]: value }))
 
-  // Warn before navigating away mid-quiz
-  const safeNavigate = (targetIdx) => {
-    if (Object.keys(answers).length > 0 && attemptId) {
-      const confirmed = window.confirm(
-        'You have answered some questions.\n\n• OK — go back (progress saved so far)\n• Cancel — stay on current question'
-      )
-      if (!confirmed) return
-    }
-    setCurrentIdx(targetIdx)
-  }
+  const safeNavigate = (targetIdx) => setCurrentIdx(targetIdx)
 
   const handleSubmit = useCallback(async (autoSubmit = false) => {
     if (!attemptId || submitting) return
     if (!autoSubmit && Object.keys(answers).length === 0) {
-      if (!window.confirm('You haven\'t answered any questions. Submit anyway?')) return
+      showToast('No answers selected — submitting with 0 answered.')
+      await new Promise(r => setTimeout(r, 1200))
     }
     clearInterval(timerRef.current)
     setSubmitting(true)
@@ -251,6 +239,17 @@ useEffect(() => {
 
   return (
     <div className="quiz-bottom">
+      {toast && (
+        <div style={{
+          position: 'fixed', bottom: 24, left: '50%', transform: 'translateX(-50%)',
+          background: 'rgba(15,23,42,0.92)', color: '#f1f5f9',
+          padding: '10px 20px', borderRadius: 24, fontSize: '0.85rem',
+          zIndex: 500, whiteSpace: 'nowrap', pointerEvents: 'none',
+          animation: 'fadeInUp 0.2s ease',
+        }}>
+          {toast}
+        </div>
+      )}
       <div className="card" style={{ marginBottom: 16 }}>
         <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', flexWrap: 'wrap', gap: 8 }}>
           <div>