Function: sundayWeekStart()
sundayWeekStart(
d):CalendarDate
Defined in: src/lib/calendar/index.ts:39
The Sunday that starts the week (Sunday→Saturday) containing d. Legacy US-week helper: billing
unified onto the Mon–Sun mondayWeekStart week (ADR-0044), so nothing keys on this anymore.
Kept only for the optional weekStartsOn: 'sunday' path and historical tests.
ponytail: delete once the 'sunday' option is dropped from recentCompletedWeeks.