The idempotent upgrade only created missing object stores, so bumping
DATA_VERSION no longer reset bad or stale data — it just added stores. This
restores a bump as a true global cache flush: the upgrade now clears every
existing store before recreating any missing ones, so shipping a version
bump forces all clients to refetch fresh on next boot.
Gated on oldVersion > 0 so fresh installs skip the flush, and clearing
before creating means only pre-existing stores are touched. This is the
break-glass lever for the one non-self-healing failure mode (non-empty
store holding wrong-shaped data paired with a matching cache key), e.g.
after a serializer shape change shipped without a version bump.
Shivam Mishra
5cb517612f