main's requirements.txt unpins asyncua (PR #30), so CI installs 2.0.1,
where DataValue's field was renamed StatusCode_ -> StatusCode. The old
kwarg made every OPC write raise TypeError at runtime - masked locally
by a stale asyncua 1.0.6 in the dev conda env. Also uses ua.DateTime
(a datetime subclass) and ua.UInt32 to satisfy the new stricter types,
with no behavior change (verified via binary encode/decode round-trip).
