Replace the bare TCP-connect return in OpcUaClientDriverProbe with a real
OPC UA GetEndpoints discovery handshake (mirroring SelectMatchingEndpointAsync
in the driver). TCP preflight still fast-fails closed ports; the handshake
confirms the remote is actually an OPC UA server, so a live-but-rejecting
non-OPC-UA process now reads RED instead of a false-healthy green.
Cheap-and-fast probe: open TCP socket to the configured endpoint,
close immediately. Surfaces SocketError on failure, latency on
success, "timed out" on caller cancel. Sufficient for the AdminUI
Test Connect "can we reach the host?" question. Richer protocol-
level probes (OPC UA session open, FOCAS handshake, gRPC ping)
are a documented follow-up. Each probe registered as
AddSingleton<IDriverProbe, X> in DriverFactoryBootstrap so they
flow through DI into AdminOperationsActor.
Historian.Wonderware returns a clean "TCP probe not applicable"
result because it communicates over a Windows named pipe, not TCP.
Also adds OpcUaClient + Historian.Wonderware.Client project
references to Host.csproj (both were missing from the driver
ItemGroup).
Joseph Doherty