/**
 * Safely resolve a user-supplied directory path, ensuring it stays within the
 * project root (sandbox). Returns the resolved absolute path, or null if the
 * path escapes the sandbox.
 *
 * Security rules:
 * - Absolute paths are rejected (must be relative to projectRoot)
 * - Leading backslashes and Windows drive roots are rejected cross-platform
 * - Resolved path must start with projectRoot (prevents `../../` traversal)
 *
 * @param dir - User-supplied directory path (from config)
 * @param projectRoot - Project root to resolve relative paths against and sandbox within
 * @returns Resolved absolute path, or null if the path is rejected
 */
export declare function resolveSafePath(dir: string, projectRoot: string): string | null;