fix: 上一题/下一题不再调 AI API，改为保存后关闭并推进索引

src/components/ResultDrawer.vue

@@ -9,9 +9,9 @@
       <div class="drawer-body" v-if="gradingStore.currentResult">
         <div class="error-message" v-if="errorMsg">{{ errorMsg }}</div>
         <div class="question-nav" v-if="questions.length > 1">
-          <el-button size="small" @click="prevQuestion" :disabled="isGrading">上一题</el-button>
+          <el-button size="small" @click="prevQuestion">上一题</el-button>
           <span class="question-indicator">{{ currentIdx + 1 }} / {{ questions.length }}</span>
-          <el-button size="small" @click="nextQuestion" :disabled="isGrading">{{ currentIdx === questions.length - 1 ? '回到首题' : '下一题' }}</el-button>
+          <el-button size="small" @click="nextQuestion">{{ currentIdx === questions.length - 1 ? '回到首题' : '下一题' }}</el-button>
         </div>
 
         <div class="question-title" v-if="currentQuestion.questionTitle">
@@ -153,7 +153,6 @@ async function gradeAt(idx: number) {
     gradingStore.setResult(result)
     currentIdx.value = idx
     gradingStore.setCurrentQuestionIndex(idx)
-    // update grading bridge
     await window.electronAPI?.grading.storeData({
       result,
       image: gradingStore.currentImage,
@@ -170,12 +169,30 @@ async function gradeAt(idx: number) {
 
 async function nextQuestion() {
   const next = (currentIdx.value + 1) % questions.value.length
-  await gradeAt(next)
+  await saveAndAdvance(next)
 }
 
 async function prevQuestion() {
   const prev = (currentIdx.value - 1 + questions.value.length) % questions.value.length
-  await gradeAt(prev)
+  await saveAndAdvance(prev)
+}
+
+async function saveAndAdvance(targetIdx: number) {
+  try {
+    await window.electronAPI.grading.submit({
+      questionId: 0,
+      imagePath: '',
+      aiScore: gradingStore.currentResult?.score ?? 0,
+      teacherScore: teacherScore.value,
+      confidence: gradingStore.currentResult?.confidence ?? 0,
+      studentAnswer: ''
+    })
+    await window.electronAPI?.rubric.setNextIndex(targetIdx)
+    gradingStore.reset()
+    closeDrawer()
+  } catch (err) {
+    ElMessage.error('保存失败：' + (err as Error).message)
+  }
 }
 
 async function reGrade() {