/**
 * Parse a strict RFC 3339 datetime string into a zoned ISO 8601 datetime
 * string.
 *
 * - Accepts `T`, `t`, or a single space as the date/time separator (all
 *   three are valid RFC 3339, unlike GMT's own zoned strings which always
 *   use `T`) and either `Z`/`z` or a numeric `±HH:MM` offset.
 * - RFC 3339 carries no IANA zone name, so the parsed offset becomes the
 *   result's time zone identifier too (e.g. `Z` → `+00:00[+00:00]`) — the
 *   same fixed-offset-as-zone convention `parseRfc2822` uses.
 * - Rejects GMT's own bracketed zoned strings (`...+00:00[UTC]`) — that
 *   annotation is not valid RFC 3339 input; use `Temporal.ZonedDateTime.from`
 *   / `isValidZonedDateTime` directly for GMT's native format instead.
 *
 * @param value RFC 3339 datetime string (e.g. "2024-03-15T14:30:00-04:00")
 * @returns zoned ISO 8601 datetime string, or "" on invalid input
 *
 * @example parseRfc3339("2024-03-15T14:30:00-04:00") // "2024-03-15T14:30:00-04:00[-04:00]"
 * @example parseRfc3339("2024-03-15T14:30:00Z") // "2024-03-15T14:30:00+00:00[+00:00]"
 * @example parseRfc3339("2024-03-15T14:30:00+00:00[UTC]") // "" (bracket annotation not valid RFC 3339)
 * @example parseRfc3339("not a date") // ""
 */
export declare function parseRfc3339(value: string): string;