feat(mtconnect): serve TIME_SERIES observations as variable-length double[] (#627)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/MTConnectTagConfigModel.cs

@@ -229,10 +229,25 @@ public sealed class MTConnectTagConfigModel
     ///     passed as null; it can only DEMOTE an item to String (DATA_SET/TABLE), which cannot create a false
     ///     warning because a numeric declaration on a String-inferred item is warned either way, and a SAMPLE
     ///     inferred Float64 is only warned about for a non-numeric, non-String declaration or an integer one.
-    ///     TIME_SERIES arrays are not detectable without it and are not covered.
+    ///     TIME_SERIES arrays are covered separately by the isArray rule in <see cref="Warnings"/>.
     /// </remarks>
     /// <returns>Zero or more human-readable warnings.</returns>
     public IReadOnlyList<string> Warnings()
+    {
+        // #627: an array (TIME_SERIES) tag is served as double[] only. Independent of the probe metadata —
+        // the array flag is authored on the tag, and any other declared element type reads BadNotSupported.
+        var arrayWarning = _bag.TryGetPropertyValue("isArray", out var arr)
+                           && arr is JsonValue av && av.TryGetValue<bool>(out var isArray) && isArray
+                           && DataType != DriverDataType.Float64
+            ? $"Data type {DataType} on an array tag: MTConnect TIME_SERIES arrays are served as Float64 (double[]) only; "
+              + "declare Float64 or the tag reads BadNotSupported. Saving is still allowed."
+            : null;
+
+        var scalar = ScalarWarnings();
+        return arrayWarning is null ? scalar : [arrayWarning, .. scalar];
+    }
+
+    private IReadOnlyList<string> ScalarWarnings()
     {
         if (string.IsNullOrWhiteSpace(MtCategory)) { return []; }