feat(adminops): IDriverProbe + TestDriverConnect actor handler

- IDriverProbe abstraction in Core.Abstractions; one impl per driver
  type, resolved by DriverType string. Phase 7.3 + 7.4 add concrete
  probes for the 9 supported driver types.
- TestDriverConnect / TestDriverConnectResult messages.
- AdminOperationsActor.HandleTestDriverConnectAsync looks up the probe
  by DriverType, runs it with a [1,60]s clamped timeout, and returns
  success/latency or failure/message. Probes that throw or time out
  surface as soft failures.

src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/IDriverProbe.cs

@@ -0,0 +1,27 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Test-connect probe for one driver type. Implementations deserialize a driver-config
+///     JSON, attempt a cheap connection (TCP open, OPC UA session, gRPC ping — whatever the
+///     driver's native protocol supports), and report success/failure with latency. Probes
+///     MUST NOT mutate any persistent state; the AdminUI invokes them against transient
+///     config from the typed form, NOT against the persisted DriverInstance row.
+/// </summary>
+public interface IDriverProbe
+{
+    /// <summary>DriverInstance.DriverType string this probe handles. Used for DI lookup.</summary>
+    string DriverType { get; }
+
+    /// <summary>
+    ///     Run the probe with the supplied config + timeout. Honour <paramref name="ct"/> for
+    ///     timeout cancellation. Never throw on connection failure; instead return a result
+    ///     with <c>Ok = false</c> + a message.
+    /// </summary>
+    Task<DriverProbeResult> ProbeAsync(string configJson, TimeSpan timeout, CancellationToken ct);
+}
+
+/// <summary>Outcome of a single <see cref="IDriverProbe.ProbeAsync"/> call.</summary>
+/// <param name="Ok">True iff the probe reached its target and the handshake succeeded.</param>
+/// <param name="Message">Human-readable status; null on success.</param>
+/// <param name="Latency">Wall-clock duration of the successful probe; null on failure.</param>
+public sealed record DriverProbeResult(bool Ok, string? Message, TimeSpan? Latency);