feat: 更新数据集加载错误提示，优化用户体验

src/routes/boot/+page.svelte

@@ -38,7 +38,7 @@ async function loadDataset() {
     const hasMetaFile = entries.some((entry) => entry.name === 'meta.json');
 
     if (!hasMetaFile) {
-      await message('The selected folder does not contain meta.json.', {
+      await message('The selected folder is not a valid dataset folder.', {
         kind: 'warning',
         title: 'Invalid Dataset Folder',
       });
@@ -50,7 +50,7 @@ async function loadDataset() {
     const parsedMeta: unknown = JSON.parse(metaText);
 
     if (!isDatasetMeta(parsedMeta)) {
-      await message('meta.json format is invalid and cannot be parsed as DatasetMeta.', {
+      await message('Dataset meta information is invalid.', {
         kind: 'warning',
         title: 'Invalid meta.json',
       });