Pure-Kotlin module, drawn from the duplicate reminder logic in Agendula and
Calendula: the lead-time unit model (ReminderUnit / decomposeReminderMinutes),
the per-target override model (ReminderOverride + reminderLeadFor /
applyReminderOverride) and the stored-format codec (ReminderOverrideCodec).
The codec's separators are configurable so each app keeps its on-disk format
(Agendula stores id:minutes, Calendula id=minutes) without a data migration.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
