"Delete only this event" on a recurring series wrote a cancelled
exception carrying just ORIGINAL_INSTANCE_TIME + STATUS_CANCELED. Without
DTSTART + DURATION the provider clones the master *with its RRULE intact*
and cancels the whole clone, so every other occurrence vanished, the
target survived as a "cancelled" ghost, and re-deleting toggled the
series back — exactly the reported corruption.
Anchor the exception as a single instance (DTSTART + DURATION + zone +
all-day, read from the series row) so the provider clears the inherited
RRULE and cancels only that occurrence — the same discipline the edit
path already documents (Codeberg #16). Also filter STATUS_CANCELED out of
the instances grid query so the cancelled occurrence disappears instead
of lingering as a tappable ghost (NULL status is kept — a normal event).
Extracts the exception ContentValues into a pure buildOccurrenceCancelValues
helper with JVM tests.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
