merge: MQTT browser+contracts review findings resolved (Driver.Mqtt.Browser-002..-005, Driver.Mqtt.Contracts-004..-007)

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

@@ -119,6 +119,14 @@ public sealed class MqttTagConfigModel
     ///     the key and inherit the driver's default (<c>true</c>). An absent key stays absent. Shared by
     ///     both modes — <c>MqttTagDefinitionFactory</c> reads <c>retainSeed</c> identically for Plain and
     ///     Sparkplug.
+    ///     <para>
+    ///     The <b>load</b> is lenient (a non-boolean value reads as <c>null</c>, i.e. "unset"), but the
+    ///     driver reads the key STRICTLY — <c>"retainSeed":"false"</c>, which a CSV import produces
+    ///     naturally, rejects the whole tag rather than silently taking the default, which is the
+    ///     INVERSE of that author's intent. No hand-mirrored rule is needed here for that:
+    ///     <see cref="Validate"/>'s <see cref="TagConfigParseGate"/> consult asks the driver's own reader
+    ///     about the loaded blob, so the save is blocked with the inspector's own wording.
+    ///     </para>
     /// </summary>
     public bool? RetainSeed { get; set; }