Occurrence ids carry their own start day, so moving the anchor or the
interval re-keys every occurrence and the marks under the old ids stop
being reachable. Nothing is rewritten — removeEvent makes the same trade,
and useMarkSet never removes because nothing else holds a copy — but the
reader is told the count first, the way removeGame reports blockedBy
instead of cascading.
Informs, never blocks. Renaming still costs nothing: the token is random
precisely so fixing a typo never moves an id, and movesOccurrences is what
keeps the warning off a rename and off a bare change of `until`.
cadenceLabel sits beside the form's own vocabulary so the sheet cannot
describe a rule differently from the control that set it.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
