/**
 * Shared utilities for builtin tools
 */
/**
 * Type guard for Node.js errors with code property
 */
export declare function isNodeError(error: unknown): error is NodeJS.ErrnoException;
/**
 * Get the file extension from a path, including the leading dot.
 * Returns empty string if no extension found.
 *
 * @example
 * getExtension('/path/to/file.ts') // returns '.ts'
 * getExtension('/path/to/file') // returns ''
 * getExtension('/path/to/.gitignore') // returns '' (dotfile, not extension)
 */
export declare function getExtension(filePath: string): string;
/**
 * Check if a file extension is in the allowed list.
 * Handles both formats: ['.ts', '.js'] or ['ts', 'js']
 */
export declare function isExtensionAllowed(filePath: string, allowedExtensions: string[]): boolean;
/**
 * Write a file atomically by writing to a temp file first, then renaming.
 * This prevents file corruption if the write is interrupted.
 */
export declare function atomicWriteFile(filePath: string, content: string, encoding?: BufferEncoding): Promise<void>;