Placed between Health and Logged-in User on /endpoints. The main agent
version, not the tray: both ship side by side in the payload as
agentversion and trayversion, so the wrong one is an easy pick.
Frontend only. EndpointState.to_dict() has carried agentversion all
along, so the fleet list API was already sending the field and nothing
rendered it.
Also bumped the empty-state colspan from 9/8 to 10/9. It is hardcoded
rather than derived from the header count, so it does not track a new
column on its own and silently under-spans the "No endpoints found" row
if missed.