fix(transport): transport template NativeAlarmSources — imports no longer amputate native alarm mirrors nor dangle instance overrides

New TemplateNativeAlarmSourceDto + init-only TemplateDto.NativeAlarmSources (empty
default, additive — IsInherited placeholders carried for the collision detector).
Exported in ToBundleContent, consumed in FromBundleContent + BuildTemplate, and a
new SyncTemplateNativeAlarmSourcesAsync runs the Overwrite add/update/delete child
sync with per-change audit rows. ArtifactDiff.CompareTemplate now DiffChildren over
native sources so Preview reports a NativeAlarmSources field change. Proven by an
end-to-end flatten test: an instance native-alarm-source override that dangled
pre-fix now resolves against the re-imported template source.

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntityDtos.cs

@@ -126,7 +126,39 @@ public sealed record TemplateDto(
     IReadOnlyList<TemplateAttributeDto> Attributes,
     IReadOnlyList<TemplateAlarmDto> Alarms,
     IReadOnlyList<TemplateScriptDto> Scripts,
-    IReadOnlyList<TemplateCompositionDto> Compositions);
+    IReadOnlyList<TemplateCompositionDto> Compositions)
+{
+    // Template-defined native alarm source bindings. Modeled as an init-only
+    // property with an empty default (NOT a positional ctor param) because an
+    // IReadOnlyList has no valid compile-time default for a positional
+    // parameter, and for the same forward/source-compat reasons as the
+    // site/instance arrays on BundleContentDto:
+    //   1. Forward-compat: a bundle written before native alarm sources were
+    //      transported has no NativeAlarmSources field and deserializes this to
+    //      Array.Empty<> — consumers always see an empty list, never null.
+    //   2. Source-compat: every existing positional `new TemplateDto(...)` caller
+    //      keeps compiling; producers opt in via the object-initializer.
+    // IsInherited placeholder rows ARE carried (the collision detector depends
+    // on them), mirroring how the flattener treats inherited native sources.
+    public IReadOnlyList<TemplateNativeAlarmSourceDto> NativeAlarmSources { get; init; } =
+        Array.Empty<TemplateNativeAlarmSourceDto>();
+}
+
+/// <summary>
+/// A template-defined native alarm source binding. Carries every writable field
+/// of the <c>TemplateNativeAlarmSource</c> entity, including the inheritance/lock
+/// flags, so an export→import round-trip is field-faithful and instance-level
+/// overrides of the source no longer dangle in the target environment.
+/// </summary>
+public sealed record TemplateNativeAlarmSourceDto(
+    string Name,
+    string? Description,
+    string ConnectionName,
+    string SourceReference,
+    string? ConditionFilter,
+    bool IsLocked,
+    bool IsInherited,
+    bool LockedInDerived);
 
 public sealed record TemplateAttributeDto(
     string Name,

src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntitySerializer.cs

@@ -91,7 +91,20 @@ public sealed class EntitySerializer
                         LockedInDerived: s.LockedInDerived)).ToList(),
                     Compositions: t.Compositions.Select(c => new TemplateCompositionDto(
                         InstanceName: c.InstanceName,
-                        ComposedTemplateName: templateNameById.TryGetValue(c.ComposedTemplateId, out var cn) ? cn : string.Empty)).ToList());
+                        ComposedTemplateName: templateNameById.TryGetValue(c.ComposedTemplateId, out var cn) ? cn : string.Empty)).ToList())
+                {
+                    // Native alarm sources carry ALL rows including IsInherited
+                    // placeholders — the collision detector depends on them.
+                    NativeAlarmSources = t.NativeAlarmSources.Select(n => new TemplateNativeAlarmSourceDto(
+                        Name: n.Name,
+                        Description: n.Description,
+                        ConnectionName: n.ConnectionName,
+                        SourceReference: n.SourceReference,
+                        ConditionFilter: n.ConditionFilter,
+                        IsLocked: n.IsLocked,
+                        IsInherited: n.IsInherited,
+                        LockedInDerived: n.LockedInDerived)).ToList(),
+                };
             }).ToList(),
             SharedScripts: aggregate.SharedScripts.Select(s => new SharedScriptDto(
                 Name: s.Name,
@@ -352,6 +365,20 @@ public sealed class EntitySerializer
                         LockedInDerived = s.LockedInDerived,
                     });
                 }
+                foreach (var n in dto.NativeAlarmSources)
+                {
+                    t.NativeAlarmSources.Add(new TemplateNativeAlarmSource(n.Name)
+                    {
+                        TemplateId = t.Id,
+                        Description = n.Description,
+                        ConnectionName = n.ConnectionName,
+                        SourceReference = n.SourceReference,
+                        ConditionFilter = n.ConditionFilter,
+                        IsLocked = n.IsLocked,
+                        IsInherited = n.IsInherited,
+                        LockedInDerived = n.LockedInDerived,
+                    });
+                }
                 return t;
             })
             .ToList();