DateTimeOffset bounds and elements refuse offsets beyond ±14:00 that timestamptz reads #131

DateTimeOffsetRange, its multirange and DateTimeOffsetSet refuse an offset beyond ±14:00, which timestamptz reads (PostgreSQL takes up to ±15:59). Loud (FormatException). InstantRange reads the same text. Measured on main (3ecfa10) against PostgreSQL 17.10:

DateTimeOffsetRange.Parse("[2026-01-01 10:00:00+15:00,)", null);  // FormatException
InstantRange.Parse("[2026-01-01 10:00:00+15:00,)", null);         // [2025-12-31T19:00:00Z,)

SELECT '[2026-01-01 10:00:00+15:00,)'::tstzrange, '[2026-01-01 10:00:00+15:59,)'::tstzrange;
-- ["2025-12-31 19:00:00+00",) | ["2025-12-31 18:01:00+00",)

Found by LiteralCorpusProbeTests (#123), family offset range, on DateTimeOffsetRange, RangeSet<DateTimeOffsetRange>, DateTimeOffsetSet and DateTimeOffsetSet<T>.

Authority. docs/serialization.md: the text is "the same text the server itself reads". The document already handles the analogous case — a ±HH:mm:ss offset DateTimeOffset cannot hold is read as "that instant at offset zero".

Cause. DateTimeOffset holds offsets up to ±14:00, and IsoTemporal parses with DateTimeOffset.TryParseExact.

Options. Read an offset beyond ±14:00 as the instant at offset zero, like the seconds offset; or document the refusal. Not breaking either way.