feat(historian): advertise only the backend's aggregates under AggregateFunctions (#682)

IHistorianDataSource.SupportedAggregates (default: every HistoryAggregateType)
is the one authority for both ServerCapabilities/AggregateFunctions (i=2997) and
HistoryServerCapabilities/AggregateFunctions (i=11201) and for the up-front
BadAggregateNotSupported in HistoryRead-Processed. Gateway declares
AggregateModeMapper.Served (4), SqlServer/QuestDB AggregateFamilies.Served (17),
Null none. Only the folder references are trimmed; the SDK's calculator
factories stay so live AggregateFilter subscriptions keep working.

Co-Authored-By: Claude <noreply@anthropic.com>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/GatewayHistorianDataSource.cs

@@ -132,6 +132,13 @@ public sealed class GatewayHistorianDataSource : IHistorianDataSource, IAsyncDis
     /// </remarks>
     public bool SupportsReverseEvents => false;
 
+    /// <inheritdoc />
+    /// <remarks>
+    ///     <see cref="AggregateModeMapper.Served"/> — the aggregates the gateway has a retrieval mode for (#682); every
+    ///     other member answers <c>BadAggregateNotSupported</c> and is not advertised.
+    /// </remarks>
+    public IReadOnlySet<HistoryAggregateType> SupportedAggregates => AggregateModeMapper.Served;
+
     /// <inheritdoc />
     /// <remarks>
     ///     A reverse (newest-first) read is refused with <see cref="NotSupportedException"/> — the server reports

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/Mapping/AggregateModeMapper.cs

@@ -1,3 +1,4 @@
+using System.Collections.Frozen;
 using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 
@@ -22,22 +23,38 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;
 /// </remarks>
 internal static class AggregateModeMapper
 {
+    /// <summary>
+    ///     The aggregates the gateway serves — every defined member <see cref="TryMap"/> maps, derived from it so the
+    ///     advertised set and the dispatch can never disagree. <see cref="GatewayHistorianDataSource.SupportedAggregates"/>
+    ///     returns it (#682); it is the ONLY declaration of the gateway's served set.
+    /// </summary>
+    public static readonly IReadOnlySet<HistoryAggregateType> Served =
+        Enum.GetValues<HistoryAggregateType>().Where(a => TryMap(a) is not null).ToFrozenSet();
+
     /// <summary>Maps an aggregate function to the gateway retrieval mode.</summary>
     /// <param name="aggregate">The driver-agnostic aggregate function.</param>
     /// <returns>The matching gateway <see cref="RetrievalMode"/>.</returns>
     /// <exception cref="HistoryAggregateNotSupportedException">A defined member the gateway has no retrieval mode for.</exception>
     /// <exception cref="ArgumentOutOfRangeException">An undefined enum value.</exception>
-    public static RetrievalMode ToRetrievalMode(HistoryAggregateType aggregate) => aggregate switch
+    public static RetrievalMode ToRetrievalMode(HistoryAggregateType aggregate)
+    {
+        if (TryMap(aggregate) is { } mode) return mode;
+
+        // Part 13 aggregates the gateway has no retrieval mode for (#285) — an UNDEFINED enum value is a
+        // programming error, but a defined-yet-unserved member is a normal client request the server
+        // answers with BadAggregateNotSupported.
+        if (Enum.IsDefined(aggregate)) throw new HistoryAggregateNotSupportedException(aggregate);
+        throw new ArgumentOutOfRangeException(
+            nameof(aggregate), aggregate, "Unmapped HistoryAggregateType — add a RetrievalMode mapping.");
+    }
+
+    /// <summary>The single mapping table: the retrieval mode for a served aggregate, or null.</summary>
+    private static RetrievalMode? TryMap(HistoryAggregateType aggregate) => aggregate switch
     {
         HistoryAggregateType.TimeAverage => RetrievalMode.TimeWeightedAverage,
         HistoryAggregateType.Minimum => RetrievalMode.MinimumWithTime,
         HistoryAggregateType.Maximum => RetrievalMode.MaximumWithTime,
         HistoryAggregateType.Total => RetrievalMode.Integral,
-        // Part 13 aggregates the gateway has no retrieval mode for (#285) — an UNDEFINED enum value is a
-        // programming error, but a defined-yet-unserved member is a normal client request the server
-        // answers with BadAggregateNotSupported.
-        _ when Enum.IsDefined(aggregate) => throw new HistoryAggregateNotSupportedException(aggregate),
-        _ => throw new ArgumentOutOfRangeException(
-            nameof(aggregate), aggregate, "Unmapped HistoryAggregateType — add a RetrievalMode mapping."),
+        _ => null,
     };
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.QuestDb/QuestDbHistorianDataSource.cs

@@ -359,6 +359,10 @@ public sealed class QuestDbHistorianDataSource : IHistorianDataSource
     /// <remarks>Reverse events reads are served natively (<c>ORDER BY … DESC</c>, Gitea #675).</remarks>
     public bool SupportsReverseEvents => true;
 
+    /// <inheritdoc />
+    /// <remarks>The seventeen <see cref="AggregateFamilies.Served"/> — shared with the other SQL backend (#682).</remarks>
+    public IReadOnlySet<HistoryAggregateType> SupportedAggregates => AggregateFamilies.Served;
+
 
     /// <inheritdoc />
     /// <remarks>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common/AggregateFamily.cs

@@ -1,3 +1,4 @@
+using System.Collections.Frozen;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common;
@@ -40,4 +41,12 @@ public static class AggregateFamilies
             or HistoryAggregateType.PercentGood or HistoryAggregateType.PercentBad => AggregateFamily.TimeWeighted,
         _ => null,
     };
+
+    /// <summary>
+    ///     The seventeen aggregates the SQL backends serve — every member <see cref="FamilyOf"/> assigns a family, derived
+    ///     from it so the set and the dispatch can never disagree. Both <c>SqlServerHistorianDataSource</c> and
+    ///     <c>QuestDbHistorianDataSource</c> return it as <see cref="IHistorianDataSource.SupportedAggregates"/> (#682).
+    /// </summary>
+    public static readonly IReadOnlySet<HistoryAggregateType> Served =
+        Enum.GetValues<HistoryAggregateType>().Where(a => FamilyOf(a) is not null).ToFrozenSet();
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer/SqlServerHistorianDataSource.cs

@@ -316,6 +316,10 @@ public sealed class SqlServerHistorianDataSource : IHistorianDataSource
     /// <remarks>Reverse events reads are served natively (<c>ORDER BY … DESC</c>, Gitea #675).</remarks>
     public bool SupportsReverseEvents => true;
 
+    /// <inheritdoc />
+    /// <remarks>The seventeen <see cref="AggregateFamilies.Served"/> — shared with the other SQL backend (#682).</remarks>
+    public IReadOnlySet<HistoryAggregateType> SupportedAggregates => AggregateFamilies.Served;
+
 
     /// <inheritdoc />
     /// <remarks>