fix(modbus): enforce region/type compatibility at the tag factory

P6: Coils/DiscreteInputs carry only Bool and register regions never Bool;
the factory (and so the deploy-gate Inspect and the AdminUI parse consult)
refuses a mismatch, and an absent dataType defaults per region (Bool for a
bit region). A HoldingRegisters+Bool tag used to throw out of the coalescing
planner and stall every tag of the subscription; the planner also skips any
incompatible pair defensively. The tag editor keeps the type compatible when
the region changes; the CLI refuses the pair up front. The array-write parity
test records the Coils divergence from DriverArrayWriteSupport (owned outside
this lane) as follow-up F1.

Refs #741
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagEditors/ModbusTagConfigEditor.razor

@@ -5,7 +5,7 @@
 
 <div class="row g-2">
     <div class="col-md-4"><label class="form-label">Region</label>
-        <select class="form-select form-select-sm" value="@_m.Region" @onchange="@(e => Update(() => _m.Region = ParseEnum(e.Value, ModbusRegion.HoldingRegisters)))">
+        <select class="form-select form-select-sm" value="@_m.Region" @onchange="@(e => Update(() => _m.SetRegion(ParseEnum(e.Value, ModbusRegion.HoldingRegisters))))">
             @foreach (var v in Enum.GetValues<ModbusRegion>()) { <option value="@v">@v</option> }
         </select></div>
     <div class="col-md-2"><label class="form-label">Address</label>

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

@@ -30,6 +30,19 @@ public sealed class ModbusTagConfigModel
     /// key stays absent.</summary>
     public bool? Writable { get; set; }
 
+    /// <summary>
+    ///     Changes the region and keeps the data type compatible with it (the driver refuses a bit region
+    ///     with a non-Bool type, and a register region with Bool): switching to Coils / DiscreteInputs selects
+    ///     Bool, switching from them back to a register region selects Int16.
+    /// </summary>
+    /// <param name="region">The newly selected region.</param>
+    public void SetRegion(ModbusRegion region)
+    {
+        Region = region;
+        if (!ModbusTagDefinitionFactory.IsRegionTypeCompatible(region, DataType))
+            DataType = ModbusTagDefinitionFactory.DefaultDataType(region);
+    }
+
     private JsonObject _bag = new();
 
     // The blob this model was LOADED FROM, or null when it was built by object initialiser rather than
@@ -49,7 +62,9 @@ public sealed class ModbusTagConfigModel
             _source = json ?? "",
             Region = TagConfigJson.GetEnum(o, "region", ModbusRegion.HoldingRegisters),
             Address = TagConfigJson.GetInt(o, "address"),
-            DataType = TagConfigJson.GetEnum(o, "dataType", ModbusDataType.Int16),
+            // Absent dataType defaults per region, exactly as the driver's factory does (Bool for a bit region).
+            DataType = TagConfigJson.GetEnum(o, "dataType",
+                ModbusTagDefinitionFactory.DefaultDataType(TagConfigJson.GetEnum(o, "region", ModbusRegion.HoldingRegisters))),
             ByteOrder = TagConfigJson.GetEnum(o, "byteOrder", ModbusByteOrder.BigEndian),
             BitIndex = TagConfigJson.GetInt(o, "bitIndex"),
             StringLength = TagConfigJson.GetInt(o, "stringLength"),