The calendar flashed whenever the event popup/form closed or a post-write events
refetch landed. Root cause: CalendarContent was a function component DEFINED
INSIDE CalendarShell's render and used as <CalendarContent />. A nested component
has a new identity every render, so React unmounted+remounted its whole subtree
— including <ScheduleXCalendar> — on ANY CalendarShell re-render. The earlier
Bug B work only minimized re-renders (Zustand selectors) to dodge this; the
resync-before-done fix made the post-write ['events'] refetch deliver changed
data again, so the remount/flash returned.
Fix: render the content as a plain JSX element value (const calendarContent)
referenced at both layout sites instead of a nested component type. Element
values reconcile in place across re-renders — no remount, no flash.
Lucas Berger
2e10752a59