/**
 * 群聊处理器工具函数
 *
 * 从 group.ts 提取的模块级纯函数。
 */
export declare function getHeaderValue(headers: Record<string, unknown>, name: string): string;
export declare function extractExtension(name: string): string;
export declare function normalizeExtension(ext: string): string;
export declare function extensionFromContentType(contentType: string): string;
export declare function mimeFromExtension(ext: string): string;
export declare function sanitizeFilename(name: string): string;
//# sourceMappingURL=group-utils.d.ts.map