Zero-dependency Hijri calendar engine with pluggable calendar registry.
Built-in Umm al-Qura (UAQ) and FCNA/ISNA calendar engines. Supports N
additional calendars via registerCalendar(). Pure Date.UTC arithmetic,
binary search on 184-entry UAQ table, Meeus Ch.49 new moon formula for
FCNA. 39 ESM + 20 CJS tests passing. Dual CJS/ESM build with full TypeScript
declarations.
