parse
Parse input as the given pattern. Accepts Latin digits and any non-Latin digit script registered in DigitScript (Devanagari today).
Returns null when:
length does not match
pattern.length,any year/month/day token is not numeric,
month is not in 1..12,
dayOfMonth is not in 1..32 (32 is allowed because some BS months have 32 days; tighter "real" validation that hits the converter and reports total days in month is the caller's job - usually via
NepaliSelectableDates+NepaliCalendarModel).
Delimiters must match pattern.delimiter exactly. Trailing/leading whitespace is NOT trimmed - text fields should call String.trim() first if they care.