refactor: 优化数据处理向导配置面板布局

数据集划分编辑器调整宽屏与窄屏布局，结构化预处理选项修正 flex 占满，非结构化智能预处理由开关改为复选卡片并补充可访问性标签。

frontend/src/views/data-process/create/DatasetSplitEditor.vue

@@ -128,19 +128,19 @@ function ariaLabel(label: string) {
 }
 
 .dataset-split-row {
-  align-items: stretch;
-  flex-direction: column;
+  align-items: flex-start;
 }
 
 .dataset-split-config {
   display: grid;
   gap: 10px;
+  flex: 0 0 460px;
 }
 
 .dataset-split-grid {
   display: grid;
   grid-template-columns: repeat(3, minmax(0, 1fr));
-  gap: 16px;
+  gap: 12px;
 }
 
 .dataset-split-field {
@@ -173,6 +173,15 @@ function ariaLabel(label: string) {
 }
 
 @media (max-width: 900px) {
+  .dataset-split-row {
+    flex-direction: column;
+    align-items: stretch;
+  }
+  
+  .dataset-split-config {
+    flex: auto;
+  }
+
   .dataset-split-grid {
     grid-template-columns: minmax(0, 1fr);
   }