DS3: the NEGATIVE transition. DS1/DS2 only prove the positive (cached → true). After
ClearDatasetCache the status APIs must flip back: IsDatasetCached false AND
IsDatasetCacheUpToDate false (a cleared dataset must never masquerade as up-to-date —
a stale "up to date" would suppress the refetch and serve nothing / stale data).
DS3: the NEGATIVE transition. DS1/DS2 only prove the positive (cached → true). After ClearDatasetCache the status APIs must flip back: IsDatasetCached false AND IsDatasetCacheUpToDate false (a cleared dataset must never masquerade as up-to-date — a stale "up to date" would suppress the refetch and serve nothing / stale data).