feat: aktualisiere Übungsanzeige, um synthetische Kapitel-MCs auszuschließen

frontend/src/views/social/VocabLessonView.vue

@@ -31,7 +31,7 @@
           class="tab-button"
         >
           {{ $t('socialnetwork.vocab.courses.exercises') }}
-          <span v-if="hasExercises" class="exercise-count">({{ effectiveExercises?.length || 0 }})</span>
+          <span v-if="hasExercises" class="exercise-count">({{ displayExercises?.length || 0 }})</span>
         </button>
       </div>
 
@@ -59,7 +59,7 @@
             </div>
             <div class="lesson-meta-item">
               <span class="lesson-meta-label">{{ $t('socialnetwork.vocab.courses.exerciseLoad') }}</span>
-              <strong>{{ effectiveExercises?.length || 0 }} {{ $t('socialnetwork.vocab.courses.exercisesShort') }}</strong>
+              <strong>{{ displayExercises?.length || 0 }} {{ $t('socialnetwork.vocab.courses.exercisesShort') }}</strong>
             </div>
           </div>
           <div
@@ -557,7 +557,7 @@
             <div class="exercise-flow-header__stats">
               <div class="exercise-flow-stat">
                 <span>{{ $t('socialnetwork.vocab.courses.exerciseProgressLabel') }}</span>
-                <strong>{{ exerciseCorrectCount }}/{{ effectiveExercises.length }}</strong>
+                <strong>{{ exerciseCorrectCount }}/{{ displayExercises.length }}</strong>
               </div>
               <div class="exercise-flow-stat">
                 <span>{{ $t('socialnetwork.vocab.courses.successRate') }}</span>
@@ -1367,15 +1367,30 @@ export default {
       }
       return [];
     },
+    // Visible exercises for UI counts: exclude synthetic chapter MCs (ids starting with 'syn-')
+    displayExercises() {
+      try {
+        const raw = this.effectiveExercises || [];
+        return raw.filter((e) => {
+          try {
+            return !(typeof e.id === 'string' && e.id.startsWith('syn-'));
+          } catch (err) {
+            return true;
+          }
+        });
+      } catch (e) {
+        return this.effectiveExercises || [];
+      }
+    },
     exerciseCorrectCount() {
-      return this.effectiveExercises.filter((exercise) => Boolean(this.exerciseResults[exercise.id]?.correct)).length;
+      return this.displayExercises.filter((exercise) => Boolean(this.exerciseResults[exercise.id]?.correct)).length;
     },
     exerciseAnsweredCount() {
-      return this.effectiveExercises.filter((exercise) => Boolean(this.exerciseResults[exercise.id])).length;
+      return this.displayExercises.filter((exercise) => Boolean(this.exerciseResults[exercise.id])).length;
     },
     exerciseProgressPercent() {
-      if (!this.effectiveExercises.length) return 0;
+      if (!this.displayExercises.length) return 0;
-      return Math.round((this.exerciseCorrectCount / this.effectiveExercises.length) * 100);
+      return Math.round((this.exerciseCorrectCount / this.displayExercises.length) * 100);
     },
     exerciseTargetScore() {
       return Number(this.lesson?.targetScorePercent) || 80;