/**
 * Encodes a remote form input the way SvelteKit's `convert_formdata` expects.
 * SvelteKit 3.0.0-next.14+ requires every field name to end with `/<form_id>`
 * (the un-keyed remote action id), so callers pass the id whenever they target
 * that wire format. SvelteKit 2 servers never see this encoding because they
 * ship the binary form bridge, which bypasses `FormData` entirely.
 */
export declare function to_form_data(input: unknown, form_id?: string): FormData;