refactor: 简化评测创建向导规则来源

移除已有维度/基线两种规则来源，评测创建仅保留新建维度流程并自动生成维度名称；维度名称字段回归独立创建页，表单校验改为返回精确布尔值并启用 scroll-to-error。

frontend/src/views/eval/DimensionCreateView.vue

@@ -22,7 +22,7 @@ const editId = computed(() => route.params.id as string | undefined)
 
 const evalModels = ref<ModelItem[]>([])
 
-const form = reactive<DimensionFormDraft>({
+const form = reactive<DimensionFormDraft & { name: string }>({
   name: '',
   type: '',
   description: '',
@@ -140,6 +140,9 @@ onMounted(() => {
 <template>
   <PageCard :title="isEdit ? '编辑评测维度' : '添加评测维度'">
     <el-form ref="formRef" :model="form" :rules="rules" label-width="130px" style="max-width: 760px">
+      <el-form-item label="维度名称" prop="name">
+        <el-input v-model="form.name" placeholder="请输入维度名称" maxlength="50" show-word-limit />
+      </el-form-item>
       <DimensionFormFields v-model="form" :eval-models="evalModels" />
 
       <el-form-item>