review(Driver.OpcUaClient.Browser): AttributesAsync updates LastUsedUtc

Review at HEAD 7286d320. -001: AttributesAsync now updates LastUsedUtc (IBrowseSession
contract) + test (InternalsVisibleTo+Moq added). -002 (continuation-point cancel leak)
deferred cross-cutting w/ runtime Driver.OpcUaClient.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser/OpcUaClientBrowseSession.cs

@@ -60,11 +60,16 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
     }
 
     /// <summary>The OPC UA picker treats variables as terminal leaves and does not surface
-    /// a per-attribute side-panel, so this always returns empty.</summary>
+    /// a per-attribute side-panel, so this always returns empty. <see cref="LastUsedUtc"/>
+    /// is still refreshed to honour the <see cref="IBrowseSession"/> contract and prevent
+    /// the reaper from evicting an active session that only receives attribute calls.</summary>
     /// <param name="nodeId">Ignored.</param>
     /// <param name="cancellationToken">Ignored.</param>
     public Task<IReadOnlyList<AttributeInfo>> AttributesAsync(string nodeId, CancellationToken cancellationToken)
-        => Task.FromResult<IReadOnlyList<AttributeInfo>>(Array.Empty<AttributeInfo>());
+    {
+        LastUsedUtc = DateTime.UtcNow;
+        return Task.FromResult<IReadOnlyList<AttributeInfo>>(Array.Empty<AttributeInfo>());
+    }
 
     /// <summary>Issue a single-level Browse (plus continuation-point follow-ups) under the
     /// given parent node. <see cref="Session.BrowseAsync"/> is not thread-safe, so all calls

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.csproj

@@ -14,4 +14,7 @@
         <PackageReference Include="OPCFoundation.NetStandard.Opc.Ua.Configuration" />
         <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />
     </ItemGroup>
+    <ItemGroup>
+        <InternalsVisibleTo Include="ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.Tests"/>
+    </ItemGroup>
 </Project>