test(transport): harden T5 native-source coverage — no-change zero-audit + IsInherited/LockedInDerived fidelity

Follow-up from the T5 code review: assert an idempotent Overwrite emits zero
TemplateNativeAlarmSource* audit rows, and round-trip IsInherited/LockedInDerived
as true through both the serializer and the importer BuildTemplate path.

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

tests/ZB.MOM.WW.ScadaBridge.Transport.Tests/Serialization/EntitySerializerTests.cs

@@ -215,7 +215,7 @@ public sealed class EntitySerializerTests
             SourceReference = "ns=3;s=Boiler.Alarm",
             ConditionFilter = "severity>500",
             IsLocked = true,
-            IsInherited = false,
+            IsInherited = true,
             LockedInDerived = true,
         });
 
@@ -230,6 +230,7 @@ public sealed class EntitySerializerTests
         Assert.Equal("ns=3;s=Boiler.Alarm", dtoSrc.SourceReference);
         Assert.Equal("severity>500", dtoSrc.ConditionFilter);
         Assert.True(dtoSrc.IsLocked);
+        Assert.True(dtoSrc.IsInherited);
         Assert.True(dtoSrc.LockedInDerived);
 
         var rtSrc = Assert.Single(Assert.Single(sut.FromBundleContent(dto).Templates).NativeAlarmSources);
@@ -239,6 +240,7 @@ public sealed class EntitySerializerTests
         Assert.Equal("ns=3;s=Boiler.Alarm", rtSrc.SourceReference);
         Assert.Equal("severity>500", rtSrc.ConditionFilter);
         Assert.True(rtSrc.IsLocked);
+        Assert.True(rtSrc.IsInherited);
         Assert.True(rtSrc.LockedInDerived);
     }