.U+ and .N+ timestamp patterns fail on ISO‑8601 timestamps without fractional seconds

.U+ and .N+ timestamp patterns fail on ISO‑8601 timestamps without fractional seconds: a task in LegoFlow-SWE (Harbor dataset). Observed symptom When parsing an ISO‑8601 timestamp with a format string that contains .U+ (microsecond precision) or .N+ (nanosecond precision), the parser throws an…

The task

**Observed symptom** When parsing an ISO‑8601 timestamp with a format string that contains `.U+` (microsecond precision) or `.N+` (nanosecond precision), the parser throws an error if the input string does not include a fractional‑seconds part. This happens even though the standard allows the fractional part to be…

Part of Lego-X/LegoFlow-SWE.