commit 0d58e77eea3c64864668297cee9f93a72be1f262
Author: Philip Chimento <pchimento@igalia.com>
Date:   Mon Feb 2 17:35:01 2026 -0800

    Intl Era/Month Code: Tests for PlainMonthDay reference years
    
    The reference years for the Chinese and Dangi lunisolar calendars should
    follow a hardcoded table, which is tested in the various chinese-* and
    dangi-* tests in this commit.
    
    The behaviour of `{ overflow: 'constrain' }` has changed for leap months
    that are not known for certain to ever have had 30 days, which is tested
    in chinese-month-codes.js and dangi-month-codes.js.
    
    This also tightens the test expectations for creation of PlainMonthDay
    in all other calendars, to make sure the reference years are correctly
    determined from the deterministic steps listed in the spec text.
    
    See: https://github.com/tc39/proposal-intl-era-monthcode/pull/108
    This normative change was adopted in the January 2026 TC39 plenary.