fix(authoring): CSV import accepts variable-length arrays; Plain MQTT isArray warns at authoring (lmxopcua#770)

CSV: IsArray with blank/0 ArrayLength is the variable-length shape browse-commit and the composer produce, so its own export now re-imports.
Plain MQTT: MqttTagDefinitionFactory.Inspect (the driver's parse, consulted by the authoring inspector) now advises when isArray is set on a Plain-shaped tag; Sparkplug-shaped blobs stay quiet.
Live Sparkplug array test and SDK reflection items remain open.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/RawTagCsvMapper.cs

@@ -225,11 +225,9 @@ public static class RawTagCsvMapper
                 arrayLength = (uint)n;
             }
 
-            if (TagArrayConfig.Validate(isArray, arrayLength) is { } arrErr)
-            {
-                return Invalid(rowNumber, cells, arrErr);
-            }
-
+            // No positive-length requirement (lmxopcua#770): IsArray with a blank/0 ArrayLength is a
+            // variable-length array (ArrayDimensions=[0]), which browse-commit and the composer both produce and
+            // honour, so the export of such a tag must re-import. TagArrayConfig.Validate stays the editor's rule.
             json = TagArrayConfig.Set(json, isArray, arrayLength);
 
             // Alarm flags — an alarm is authored iff Alarm.AlarmType is present.