Additive, backward-compatible (MinAgent floor unchanged). The SMART is already
computed on the request path (storage.Observe -> enrich); this copies the target's
Smart into localapi.DiskInfo (pointer, omitempty) only when Health != "", so an
unread/absent summary stays omitted and the controller renders "Nincs adat".
No new smartctl load, endpoint, or sudoers change.
Test TestDisks_SmartSerialized + red-proof (drop the copy -> fails).
