[Copilot]

A review comment identified an off-by-boundary bug: Naw-Rúz dates falling on March 20 were being assigned to the previous Bahá’í year. This PR applies the requested fix by using the computed Naw-Rúz date directly and treating only strictly earlier dates as pre-boundary.

• Boundary logic fix (bahai.from_jd)

  • Replaced the hardcoded March 20 cutoff with a strict comparison against the computed Naw-Rúz day for the Gregorian year.
  • This ensures Naw-Rúz itself is classified as day 1 of month 1 in the new Bahá’í year.

• Regression coverage alignment

  • Existing Bahá’í test expectations for 2016-03-20 -> (173, 1, 1) now pass with the corrected boundary behavior.

# before
x = 1 if jd <= gregorian.to_jd(gy, n_month, 20) else 0

# after
x = 1 if jd < gregorian.to_jd(gy, n_month, n_day) else 0