feat(lmxproxy): add DatetimeArray proto type for DateTime[] round-trip fidelity

Added DatetimeArray message (repeated int64, UTC ticks) to proto and
code-first contracts. Host serializes DateTime[] → DatetimeArray.
Client deserializes DatetimeArray → DateTime[] (not raw long[]).
Client ExtractArrayValue now unpacks all array types including DateTime.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lmxproxy/src/ZB.MOM.WW.LmxProxy.Client/Domain/ScadaContracts.cs

@@ -120,6 +120,9 @@ public class ArrayValue
 
     [DataMember(Order = 6)]
     public StringArray? StringValues { get; set; }
+
+    [DataMember(Order = 7)]
+    public DatetimeArray? DatetimeValues { get; set; }
 }
 
 [DataContract]
@@ -164,6 +167,13 @@ public class StringArray
     public List<string> Values { get; set; } = [];
 }
 
+[DataContract]
+public class DatetimeArray
+{
+    [DataMember(Order = 1)]
+    public List<long> Values { get; set; } = [];
+}
+
 // ────────────────────────────────────────────────────────────────
 // Quality Code (v2)
 // ────────────────────────────────────────────────────────────────

lmxproxy/src/ZB.MOM.WW.LmxProxy.Client/LmxProxyClient.cs

@@ -271,12 +271,30 @@ public partial class LmxProxyClient : ILmxProxyClient
             TypedValueCase.StringValue => tv.StringValue,
             TypedValueCase.BytesValue => tv.BytesValue,
             TypedValueCase.DatetimeValue => new DateTime(tv.DatetimeValue, DateTimeKind.Utc),
-            TypedValueCase.ArrayValue => tv.ArrayValue,
+            TypedValueCase.ArrayValue => ExtractArrayValue(tv.ArrayValue),
             TypedValueCase.None => null,
             _ => null
         };
     }
 
+    internal static object? ExtractArrayValue(ArrayValue? av)
+    {
+        if (av is null) return null;
+        if (av.BoolValues is not null) return av.BoolValues.Values.ToArray();
+        if (av.Int32Values is not null) return av.Int32Values.Values.ToArray();
+        if (av.Int64Values is not null) return av.Int64Values.Values.ToArray();
+        if (av.FloatValues is not null) return av.FloatValues.Values.ToArray();
+        if (av.DoubleValues is not null) return av.DoubleValues.Values.ToArray();
+        if (av.StringValues is not null) return av.StringValues.Values.ToArray();
+        if (av.DatetimeValues is not null)
+        {
+            return av.DatetimeValues.Values
+                .Select(ticks => new DateTime(ticks, DateTimeKind.Utc))
+                .ToArray();
+        }
+        return null;
+    }
+
     private async Task<T> ExecuteWithRetry<T>(Func<Task<T>> operation, CancellationToken ct)
     {
         if (_resiliencePipeline is not null)

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Domain/TypedValueConverter.cs

@@ -109,9 +109,9 @@ namespace ZB.MOM.WW.LmxProxy.Host.Domain
 
                 case DateTime[] dtArr:
                 {
-                    var arr = new Scada.Int64Array();
+                    var arr = new Scada.DatetimeArray();
                     arr.Values.AddRange(Array.ConvertAll(dtArr, dt => dt.ToUniversalTime().Ticks));
-                    return new Scada.TypedValue { ArrayValue = new Scada.ArrayValue { Int64Values = arr } };
+                    return new Scada.TypedValue { ArrayValue = new Scada.ArrayValue { DatetimeValues = arr } };
                 }
 
                 default:
@@ -202,6 +202,17 @@ namespace ZB.MOM.WW.LmxProxy.Host.Domain
                         ? ToArray(arrayValue.StringValues.Values)
                         : Array.Empty<string>();
 
+                case Scada.ArrayValue.ValuesOneofCase.DatetimeValues:
+                    if (arrayValue.DatetimeValues?.Values?.Count > 0)
+                    {
+                        var ticks = ToArray(arrayValue.DatetimeValues.Values);
+                        var result = new DateTime[ticks.Length];
+                        for (int i = 0; i < ticks.Length; i++)
+                            result[i] = new DateTime(ticks[i], DateTimeKind.Utc);
+                        return result;
+                    }
+                    return Array.Empty<DateTime>();
+
                 default:
                     return null;
             }

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Grpc/Protos/scada.proto

@@ -38,21 +38,23 @@ message TypedValue {
 
 message ArrayValue {
   oneof values {
-    BoolArray   bool_values   = 1;
+    BoolArray     bool_values     = 1;
-    Int32Array  int32_values  = 2;
+    Int32Array    int32_values    = 2;
-    Int64Array  int64_values  = 3;
+    Int64Array    int64_values    = 3;
-    FloatArray  float_values  = 4;
+    FloatArray    float_values    = 4;
-    DoubleArray double_values = 5;
+    DoubleArray   double_values   = 5;
-    StringArray string_values = 6;
+    StringArray   string_values   = 6;
+    DatetimeArray datetime_values = 7;   // UTC DateTime.Ticks arrays
   }
 }
 
-message BoolArray   { repeated bool   values = 1; }
+message BoolArray     { repeated bool   values = 1; }
-message Int32Array  { repeated int32  values = 1; }
+message Int32Array    { repeated int32  values = 1; }
-message Int64Array  { repeated int64  values = 1; }
+message Int64Array    { repeated int64  values = 1; }
-message FloatArray  { repeated float  values = 1; }
+message FloatArray    { repeated float  values = 1; }
-message DoubleArray { repeated double values = 1; }
+message DoubleArray   { repeated double values = 1; }
-message StringArray { repeated string values = 1; }
+message StringArray   { repeated string values = 1; }
+message DatetimeArray { repeated int64  values = 1; }  // UTC DateTime.Ticks
 
 // ============================================================
 // OPC UA-Style Quality Codes