fix(frontend): remove practice sample fill action

frontend/src/views/train/practice.vue

@@ -118,16 +118,8 @@
           <div class="reply-box">
             <div class="reply-head">
               <span>学员下一句</span>
-              <el-button text type="danger" :disabled="finished" @click="fillReferenceReply">填入参考回复</el-button>
             </div>
-            <el-input
+            <el-input v-model="draftReply" type="textarea" :rows="5" resize="none" :disabled="finished" placeholder="输入学员真实回复" />
-              v-model="draftReply"
-              type="textarea"
-              :rows="5"
-              resize="none"
-              :disabled="finished"
-              placeholder="输入学员回复，或点击“填入参考回复”推进测试"
-            />
           </div>
 
           <div class="action-row">
@@ -673,10 +665,6 @@ const startPractice = async () => {
   started.value = true;
 };
 
-const fillReferenceReply = () => {
-  draftReply.value = selectedScenario.value.rounds[activeRound.value].sampleReply;
-};
-
 const continueRound = async () => {
   const round = selectedScenario.value.rounds[activeRound.value];
   if (!draftReply.value.trim()) {