fix(templates): override rows on a derived template are not second definitions in the collision check (ScadaBridge#119)

CollisionDetector counted a derived template's own override row (same name as a
parent member, IsInherited=false) as a second definition alongside the
parent's row, so AddAttribute/AddAlarm/AddScript for a fresh name failed with a
false "Naming collision" once any override existed. The inheritance walk now
keeps a (type, name) shadow set: a member defined at a nearer level of the
chain shadows the same member further up (effective member set, by name),
including overrides at mid levels. Real collisions (e.g. against a composed
module) still report.

Regression tests in TemplateEngine.Tests (detector + service, attribute/alarm/
script, mid-level override, positive control); 6 fail without the fix.
The #118 importer's additions-before-overrides ordering is now unnecessary but
harmless and was left in place.

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

src/ZB.MOM.WW.ScadaBridge.TemplateEngine/CollisionDetector.cs

@@ -36,7 +36,11 @@ public static class CollisionDetector
 
         // Collect direct (top-level) members. Inherited placeholder rows are skipped:
         // the inheritance walk below re-adds them under the parent's origin.
-        CollectDirectMembers(template, prefix: null, originPrefix: template.Name, allMembers, skipInherited: true);
+        // Names defined by a nearer level of the chain shadow the same (type, name) further
+        // up: an own row sharing a parent member's name is an OVERRIDE of it (the effective
+        // member set holds the name once), not a second definition (ScadaBridge#119).
+        var shadowed = new HashSet<(string Type, string Name)>();
+        CollectDirectMembers(template, prefix: null, originPrefix: template.Name, allMembers, skipInherited: true, shadowed);
 
         // Collect members from composed modules recursively
         foreach (var composition in template.Compositions)
@@ -53,7 +57,7 @@ public static class CollisionDetector
         }
 
         // Collect inherited members (walk parent chain)
-        CollectInheritedMembers(template, lookup, allMembers, moduleMemo, new HashSet<int> { template.Id });
+        CollectInheritedMembers(template, lookup, allMembers, moduleMemo, new HashSet<int> { template.Id }, shadowed);
 
         // Detect duplicates by canonical name
         var collisions = new List<string>();
@@ -93,28 +97,43 @@ public static class CollisionDetector
         string? prefix,
         string originPrefix,
         List<ResolvedMember> members,
-        bool skipInherited)
+        bool skipInherited,
+        HashSet<(string Type, string Name)>? shadowed = null)
     {
+        // Rows shadowed by a nearer level are skipped; this level's own names are only
+        // added to the shadow set afterwards so same-level duplicates stay visible.
+        var levelKeys = new List<(string, string)>();
+        bool Skip(string type, string name, bool inherited)
+        {
+            if (skipInherited && inherited) return true;
+            if (shadowed != null && shadowed.Contains((type, name))) return true;
+            levelKeys.Add((type, name));
+            return false;
+        }
+
         foreach (var attr in template.Attributes)
         {
-            if (skipInherited && attr.IsInherited) continue;
+            if (Skip("Attribute", attr.Name, attr.IsInherited)) continue;
             var canonicalName = prefix == null ? attr.Name : $"{prefix}.{attr.Name}";
             members.Add(new ResolvedMember(canonicalName, "Attribute", originPrefix));
         }
 
         foreach (var alarm in template.Alarms)
         {
-            if (skipInherited && alarm.IsInherited) continue;
+            if (Skip("Alarm", alarm.Name, alarm.IsInherited)) continue;
             var canonicalName = prefix == null ? alarm.Name : $"{prefix}.{alarm.Name}";
             members.Add(new ResolvedMember(canonicalName, "Alarm", originPrefix));
         }
 
         foreach (var script in template.Scripts)
         {
-            if (skipInherited && script.IsInherited) continue;
+            if (Skip("Script", script.Name, script.IsInherited)) continue;
             var canonicalName = prefix == null ? script.Name : $"{prefix}.{script.Name}";
             members.Add(new ResolvedMember(canonicalName, "Script", originPrefix));
         }
+
+        if (shadowed != null)
+            foreach (var k in levelKeys) shadowed.Add(k);
     }
 
     /// <summary>
@@ -234,7 +253,8 @@ public static class CollisionDetector
         Dictionary<int, Template> lookup,
         List<ResolvedMember> members,
         Dictionary<int, IReadOnlyList<RelativeMember>> moduleMemo,
-        HashSet<int> visited)
+        HashSet<int> visited,
+        HashSet<(string Type, string Name)> shadowed)
     {
         if (!template.ParentTemplateId.HasValue)
             return;
@@ -248,7 +268,7 @@ public static class CollisionDetector
         // Inherited direct members (no prefix). Skip the parent's OWN inherited
         // placeholders too: the next recursion adds the grandparent's real rows, so
         // counting the parent's copies would re-introduce the collision one level up.
-        CollectDirectMembers(parent, prefix: null, $"parent '{parent.Name}'", members, skipInherited: true);
+        CollectDirectMembers(parent, prefix: null, $"parent '{parent.Name}'", members, skipInherited: true, shadowed);
 
         // Inherited composed modules
         foreach (var composition in parent.Compositions)
@@ -265,6 +285,6 @@ public static class CollisionDetector
         }
 
         // Continue up the inheritance chain
-        CollectInheritedMembers(parent, lookup, members, moduleMemo, visited);
+        CollectInheritedMembers(parent, lookup, members, moduleMemo, visited, shadowed);
     }
 }