DriverTestConnectButton always sent a fixed 10 s, and the Galaxy/OpcUaClient
probes run under min(caller, configured), so ProbeTimeoutSeconds - documented
on every driver as the Test Connect timeout - could shorten a probe but never
lengthen it (Galaxy's 30 s default was silently 10 s). TestConnectBudget reads
the root ProbeTimeoutSeconds from the merged config at click time, clamped to
the actor's [1, 60] s, falling back to TimeoutSeconds. DeviceModal (the only
host) needs no change. The Galaxy/OpcUaClient form hints are reworded.
The 30 s result-clear timer moves from System.Timers.Timer + an async void
Elapsed lambda to System.Threading.Timer, drained in DisposeAsync, with a
generation so a superseded fire cannot clear a newer result.
Refs #745
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty