fix(historian-gateway): seam maxEvents XML doc + driver Platforms + ValueTask in fake

Addresses Task 1 code-review: document that ReadEventsAsync.maxEvents is enforced
client-side (no server cap in the wire contract); add Platforms=AnyCPU;x64 to match
sibling drivers; use ValueTask.CompletedTask in FakeHistorianGatewayClient.

Claude-Session: https://claude.ai/code/session_012SDSQ3AcaXqPcBtDESBRii

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

@@ -35,6 +35,16 @@ public interface IHistorianGatewayClient : IAsyncDisposable
         CancellationToken ct);
 
     /// <summary>Streams historian events over a window, optionally filtered to a single source name.</summary>
+    /// <param name="sourceName">Optional source-name filter; <c>null</c> returns events from all sources.</param>
+    /// <param name="startUtc">Inclusive start of the time window (UTC).</param>
+    /// <param name="endUtc">Exclusive end of the time window (UTC).</param>
+    /// <param name="maxEvents">
+    /// Caps the number of events returned. The gateway wire contract (<c>ReadEventsRequest</c>) has
+    /// no per-call server cap, so this limit is enforced client-side by early stream termination:
+    /// <c>0</c> or negative means no client-side limit (the gateway may still apply its configured
+    /// <c>RuntimeDb:EventReadMaxRows</c>); a positive value stops draining after that many events.
+    /// </param>
+    /// <param name="ct">Cancellation token.</param>
     IAsyncEnumerable<HistorianEvent> ReadEventsAsync(
         string? sourceName,
         DateTime startUtc,

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.csproj

@@ -4,6 +4,7 @@
         <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
         <GenerateDocumentationFile>true</GenerateDocumentationFile>
         <NoWarn>$(NoWarn);CS1591</NoWarn>
+        <Platforms>AnyCPU;x64</Platforms>
         <RootNamespace>ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway</RootNamespace>
     </PropertyGroup>