feat(dcl): BrowseNext continuation paging + StubOpcUaClient canned browse (T15)

src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Protocol/IBrowsableDataConnection.cs

@@ -10,21 +10,28 @@ public interface IBrowsableDataConnection
 {
     /// <summary>
     /// Returns the immediate children of <paramref name="parentNodeId"/>, or
-    /// the server's root-level nodes when null.
+    /// the server's root-level nodes when null. Pageable: when a prior call
+    /// returned a non-null <see cref="BrowseChildrenResult.ContinuationToken"/>,
+    /// pass it back via <paramref name="continuationToken"/> to fetch the next
+    /// page; a null/empty token starts a fresh browse of <paramref name="parentNodeId"/>.
     /// </summary>
     /// <param name="parentNodeId">Node id whose children to browse, or null for the server root (OPC UA ObjectsFolder).</param>
+    /// <param name="continuationToken">Opaque token from a prior <see cref="BrowseChildrenResult.ContinuationToken"/> to fetch the next page; null/empty starts a fresh browse. The token is implementation-private (e.g. a Base64 OPC UA continuation point) and must not be interpreted by callers.</param>
     /// <param name="cancellationToken">Cancellation token; on cancellation the implementation should throw <see cref="OperationCanceledException"/>.</param>
-    /// <returns>A task that resolves to the child nodes and a flag indicating whether results were truncated.</returns>
+    /// <returns>A task that resolves to the child nodes, a flag indicating whether more results remain, and a continuation token to fetch the next page (null when exhausted).</returns>
     Task<BrowseChildrenResult> BrowseChildrenAsync(
         string? parentNodeId,
+        string? continuationToken = null,
         CancellationToken cancellationToken = default);
 }
 
 /// <param name="Children">Child nodes returned by the server in browse order.</param>
-/// <param name="Truncated">True when the server reported more children than the per-call cap; remaining children must be discovered via manual entry.</param>
+/// <param name="Truncated">True when more children remain beyond this page; fetch them by passing <paramref name="ContinuationToken"/> back to <see cref="IBrowsableDataConnection.BrowseChildrenAsync"/>.</param>
+/// <param name="ContinuationToken">Opaque token to fetch the next page (echo it back via the <c>continuationToken</c> parameter), or null when the browse is exhausted. Implementation-private — callers must treat it as opaque.</param>
 public record BrowseChildrenResult(
     IReadOnlyList<BrowseNode> Children,
-    bool Truncated);
+    bool Truncated,
+    string? ContinuationToken = null);
 
 /// <param name="NodeId">Server-issued node identifier (e.g. <c>"ns=2;s=Devices.Pump1.Speed"</c>).</param>
 /// <param name="DisplayName">Human-readable display name from the server's DisplayName attribute.</param>