Auto: abcip-4.2 — write deadband / write-on-change

Closes #239

src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriverFactoryExtensions.cs

@@ -86,7 +86,11 @@ public static class AbCipDriverFactoryExtensions
                 : null,
             SafetyTag: t.SafetyTag ?? false,
             // PR abcip-4.1 — per-tag scan rate override; null means "use subscription default".
-            ScanRateMs: t.ScanRateMs);
+            ScanRateMs: t.ScanRateMs,
+            // PR abcip-4.2 — per-tag write-deadband + write-on-change. Both default to "off"
+            // when absent so back-compat deployments behave exactly as before.
+            WriteDeadband: t.WriteDeadband,
+            WriteOnChange: t.WriteOnChange ?? false);
 
     private static T ParseEnum<T>(string? raw, string? tagName, string driverInstanceId, string field,
         T? fallback = null) where T : struct, Enum
@@ -180,6 +184,22 @@ public static class AbCipDriverFactoryExtensions
         ///     that don't set the knob. Mirrors Kepware's "scan classes" model.
         /// </summary>
         public int? ScanRateMs { get; init; }
+
+        /// <summary>
+        ///     PR abcip-4.2 — optional numeric write deadband. When set, the driver skips a
+        ///     wire write whose absolute difference from the previous successfully-written
+        ///     value falls below this threshold. Suppressed writes still return <c>Good</c>.
+        ///     <c>null</c> = no numeric suppression (back-compat default).
+        /// </summary>
+        public double? WriteDeadband { get; init; }
+
+        /// <summary>
+        ///     PR abcip-4.2 — optional write-on-change gate. When <c>true</c>, the driver
+        ///     skips a wire write whose value equals the previous successfully-written value.
+        ///     Combines with <see cref="WriteDeadband"/> on numeric tags (deadband path takes
+        ///     priority for numerics). Default <c>false</c> — every write reaches the wire.
+        /// </summary>
+        public bool? WriteOnChange { get; init; }
     }
 
     internal sealed class AbCipMemberDto