Grace extensions overwrote ExpiresAt, so a polled stale entry never hit
MaxGracePeriod. The bound now uses the first expiry.
SetMaxSize with a non-positive size spun the eviction loop forever. It
now clamps to 1.
One value larger than MaxMemoryBytes flushed every other entry and left
the cache over its cap. The cache now drops that value.
int64(float64) wrapped a far-future nbf or iat into the past, so the
token passed. Non-finite and out-of-range claims now fail.
