/**
 * Restrict a file to its owner, for real, on every platform.
 *
 * The codebase applied `chmod(path, 0o600)` to credential files, but on Windows
 * chmod maps only to the read-only attribute and does nothing to the ACL — a
 * reader of the source reasonably concludes the file is owner-restricted when it
 * is not (SKY-106). On win32 this strips inheritance and grants only the current
 * user; on posix it keeps the existing 0o600.
 *
 * Best-effort: a failure must never break a config or credential write, so
 * errors are swallowed. Intended for infrequent writes (config, identity) — not
 * hot paths, since the win32 branch spawns icacls.
 */
export declare function restrictToOwner(filePath: string): void;