test: 优化测试代码

- 显式导入相关依赖以避免相关问题

server/utils/object.test.ts

@@ -1,4 +1,5 @@
 import { expect, test, describe } from 'vitest';
+import { isObject, isArrayOfObject } from './object';
 
 /**
  * 单元测试: isObject

server/utils/search-converters.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, test } from 'vitest';
+import { converters } from './search-converters';
 
 /**
  * 单元测试: converters
@@ -69,7 +70,7 @@ describe('converters', () => {
     expect(result).toEqual({
       id: 'TEST-UUID',
       title: 'User Manual',
-      summary: undefined,
+      summary: '',
       type: 'document',
     });
   });