Auto: ablegacy-12 — auto-demote on comm failure

Closes #255

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

@@ -38,4 +38,16 @@ public sealed record HostStatusChangedEventArgs(
     HostState NewState);
 
 /// <summary>Host lifecycle state. Generalization of Galaxy's Platform/Engine ScanState.</summary>
-public enum HostState { Unknown, Running, Stopped, Faulted }
+/// <remarks>
+///     <para>
+///         <see cref="Demoted"/> (PR ablegacy-12 / #255) is a soft-stopped state used by drivers
+///         that auto-throttle a host after N consecutive comm failures. Reads are short-circuited
+///         with <c>BadCommunicationError</c> for a configurable cool-down window so one slow PLC
+///         doesn't starve faster peers sharing the same driver. Demoted is *not* the same as
+///         <see cref="Stopped"/> (which means "probe says it's down") nor <see cref="Faulted"/>
+///         (which means "the driver itself is broken"); it's a deliberate driver-side back-off.
+///         Consumers that don't recognize <c>Demoted</c> can safely treat it as <c>Stopped</c>
+///         (see <c>HostStatusPublisher.MapState</c>).
+///     </para>
+/// </remarks>
+public enum HostState { Unknown, Running, Stopped, Faulted, Demoted }