Pure, testable core of the prefill: payload + config -> flat values ready to
lay down. What the machine does not know stays empty and is listed in
aCompleter, never invented (no fake 00:00, no made-up coordinates).
DTEND is exclusive (RFC 5545): a festival on the 18th-20th carries DTEND=21,
so the end date must step back one day, in local components for all-day
events. Without it, a wrong date reaches a moderated form.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
