feat(vocab-lesson): enhance exercise navigation and randomization logic

- Improved the exercise progression logic to automatically advance only on correct answers, ensuring better user feedback during learning.
- Added a new method to shuffle multiple-choice options display order when distractor replacement is not applicable, enhancing the exercise experience.
- Updated the build process for randomized options to include both randomization from a pool and display order shuffling, improving overall engagement and learning outcomes.

frontend/src/views/social/VocabLessonView.vue

@@ -2031,7 +2031,15 @@ export default {
         if (this.sequentialPanelActive) {
           const list = this.scrambledChapterExamExercises;
           const idx = list.findIndex((e) => e.id === exerciseId);
-          if (idx >= 0 && idx < list.length - 1 && this.exerciseResults[exerciseId]) {
+          const result = this.exerciseResults[exerciseId];
+          // Nur bei richtiger Antwort automatisch weiter: Bei Fehler bleibt die Karte sichtbar,
+          // damit „Falsch“ und die Musterlösung angezeigt werden; Weiter geht es per Nav-Button.
+          if (
+            idx >= 0
+            && idx < list.length - 1
+            && result
+            && result.correct
+          ) {
             this.exerciseSequentialIndex = idx + 1;
           }
         }
@@ -2630,15 +2638,38 @@ export default {
       const all = this._shuffleArray([...correctTexts, ...picked]);
       return { options: all, useTextAnswer: true };
     },
+    /**
+     * Wenn keine Distraktor-Ersetzung läuft (z. B. answerLanguage fehlt), nur die gegebenen
+     * Optionen mischen. Richtige Antwort bleibt über Optionstext prüfbar (useTextAnswer).
+     */
+    shuffleMcOptionsDisplayOrder(exercise) {
+      const q = this.getQuestionData(exercise);
+      if (!q || q.type !== 'multiple_choice' || q.randomizeDistractors === false) {
+        return null;
+      }
+      const options = q.options || [];
+      if (options.length < 2) {
+        return null;
+      }
+      return {
+        options: this._shuffleArray(options),
+        useTextAnswer: true
+      };
+    },
     buildMcRandomizedOptions() {
       this.mcRandomizedOptions = {};
       const exercises = this.effectiveExercises;
       if (!exercises) return;
       exercises.forEach((ex) => {
         if (this.getExerciseType(ex) !== 'multiple_choice') return;
-        const built = this.randomizeMcOptionsIfPossible(ex);
-        if (built) {
-          this.mcRandomizedOptions[ex.id] = built;
+        const fromPool = this.randomizeMcOptionsIfPossible(ex);
+        if (fromPool) {
+          this.mcRandomizedOptions[ex.id] = fromPool;
+          return;
+        }
+        const orderOnly = this.shuffleMcOptionsDisplayOrder(ex);
+        if (orderOnly) {
+          this.mcRandomizedOptions[ex.id] = orderOnly;
         }
       });
     },