fix(templates): gate resolver HiLo-merge on both-HiLo to match flattener (#262)

Change `mergeEffective` delegate in `ResolveWinners<T>` from `Func<string?, T, string?>`
to `Func<Winner<T>, T, string?>` so the alarm hook can inspect the existing winner's row.
Gate the per-setpoint merge in `ResolveAlarmWinners` on both sides being HiLo
(`existingWinner.Row.TriggerType == HiLo && derived.TriggerType == HiLo`), matching
`FlatteningService.ResolveInheritedAlarms` exactly. Base non-HiLo + derived HiLo now
falls through to whole-replace (derived config verbatim) — the same path the flattener
takes. Preview-only fix; the deploy path is unchanged.

Add test: `Resolve_BaseNonHiLo_DerivedHiLo_DerivedConfigWinsVerbatim` — asserts
resolver and flattener agree when base is ValueMatch and derived overrides to HiLo.

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

@@ -111,8 +111,10 @@ public static class TemplateInheritanceResolver
     /// effective value when a derived row OVERRIDES an existing winner -- for HiLo
     /// alarms this reuses <see cref="FlatteningService.MergeHiLoConfig"/>
     /// so a partial override (e.g. just <c>hi</c>) inherits the rest of the
-    /// ancestor config, exactly as deploy does. When null, the winning row's own
-    /// value is used verbatim (whole-replace).
+    /// ancestor config, exactly as deploy does. The full existing <see cref="Winner{T}"/>
+    /// is passed so the hook can inspect the inherited row's fields (e.g.
+    /// <c>TriggerType</c>) before deciding whether to merge or whole-replace.
+    /// When null, the winning row's own value is used verbatim (whole-replace).
     /// </para>
     /// </summary>
     private static Dictionary<string, Winner<T>> ResolveWinners<T>(
@@ -123,7 +125,7 @@ public static class TemplateInheritanceResolver
         Func<T, bool> isLocked,
         Func<T, bool> lockedInDerived,
         Func<T, string?> valueOf,
-        Func<string?, T, string?>? mergeEffective = null)
+        Func<Winner<T>, T, string?>? mergeEffective = null)
     {
         var result = new Dictionary<string, Winner<T>>(StringComparer.Ordinal);
 
@@ -158,7 +160,7 @@ public static class TemplateInheritanceResolver
                 // hook a chance to fuse the two effective values (HiLo per-setpoint);
                 // otherwise the overriding row's own value wins (whole-replace).
                 var effective = existing != null && mergeEffective != null
-                    ? mergeEffective(existing.EffectiveValue, row)
+                    ? mergeEffective(existing, row)
                     : valueOf(row);
                 result[name] = new Winner<T>(row, template, baseLocked, effective);
             }
@@ -183,8 +185,11 @@ public static class TemplateInheritanceResolver
         // Winner.EffectiveValue carries the PER-SETPOINT MERGED trigger config so
         // a partial HiLo override (e.g. just `hi`) inherits the rest from the
         // ancestor -- reusing FlatteningService.MergeHiLoConfig so the resolver
-        // preview equals deploy. Other trigger types whole-replace (mergeEffective
-        // returns the derived row's own config unchanged).
+        // preview equals deploy. The merge is gated on BOTH the existing winner
+        // AND the derived row being HiLo, matching FlatteningService.ResolveInheritedAlarms
+        // (lines: alarm.TriggerType == HiLo && existing.TriggerType == nameof(HiLo)).
+        // When only the derived side is HiLo (base is non-HiLo), derived config wins
+        // verbatim — the same whole-replace path the flattener takes in that case.
         ResolveWinners(
             chain,
             t => t.Alarms,
@@ -193,9 +198,9 @@ public static class TemplateInheritanceResolver
             a => a.IsLocked,
             a => a.LockedInDerived,
             a => a.TriggerConfiguration,
-            (existingTrigger, derived) =>
-                derived.TriggerType == AlarmTriggerType.HiLo
-                    ? FlatteningService.MergeHiLoConfig(existingTrigger, derived.TriggerConfiguration)
+            (existingWinner, derived) =>
+                existingWinner.Row.TriggerType == AlarmTriggerType.HiLo && derived.TriggerType == AlarmTriggerType.HiLo
+                    ? FlatteningService.MergeHiLoConfig(existingWinner.EffectiveValue, derived.TriggerConfiguration)
                     : derived.TriggerConfiguration);
 
     private static Dictionary<string, Winner<TemplateScript>> ResolveScriptWinners(