feat(ai): 移除 Excel 导入预检链路

- 删除 preflight_import 工具、预检卡、resolve 接口与 ui.import_preflight 事件
- 删除 imports.preflight 解析器与 PreflightReport 类型
- SYSTEM_PROMPT 改为上传 Excel 后直接确认列映射/策略并调用 start_import_wizard
- 前端同步移除预检类型/组件/测试，保留导入向导

apps/admin/src/components/AiChat/uiArtifacts.ts

@@ -60,8 +60,6 @@ export function mergeArtifactIntoMessage(
     message.reviews = mergeById<AiReviewSchema>(message.reviews, payload as AiReviewSchema);
   } else if (artifact.type === 'chart') {
     message.charts = mergeById<AiChartSchema>(message.charts, payload as AiChartSchema);
-  } else if (artifact.type === 'import_preflight') {
-    message.metadata = { ...message.metadata, a2uiImportPreflight: payload };
   } else if (artifact.type === 'import_wizard') {
     message.metadata = { ...message.metadata, a2uiImportWizard: payload };
   }