chore: 清理项目冗余文件和构建中间产物

删除根目录 index.ts（与 start 脚本重复）、移除 package.json 中无效的 module 字段、构建成功后自动清理 .build/ 目录

scripts/build.ts

@@ -52,6 +52,8 @@ if (!result.success) {
 
 console.log(`Built executable: ${executablePath}`);
 
+await rm(buildDir, { recursive: true, force: true });
+
 async function listFiles(directory: string): Promise<string[]> {
   const entries = await readdir(directory, { withFileTypes: true });
   const files = await Promise.all(