feat: thread BrowseNext continuation token through actor + BrowseService (T15)

src/ZB.MOM.WW.ScadaBridge.Commons/Messages/Management/BrowseCommands.cs

@@ -15,14 +15,30 @@ namespace ZB.MOM.WW.ScadaBridge.Commons.Messages.Management;
 /// </remarks>
 /// <param name="ConnectionName">Name of the site-local data connection to browse against.</param>
 /// <param name="ParentNodeId">Node to browse, or null to browse from the server root (ObjectsFolder).</param>
+/// <param name="ContinuationToken">
+/// Opaque adapter cursor for fetching the NEXT page of children under
+/// <see cref="ParentNodeId"/>. Null on the first request; on a subsequent
+/// request carry back the token from the prior <see cref="BrowseNodeResult.ContinuationToken"/>.
+/// Additive (appended last) so positional construction stays source-compatible.
+/// </param>
 public record BrowseNodeCommand(
     string ConnectionName,
-    string? ParentNodeId);
+    string? ParentNodeId,
+    string? ContinuationToken = null);
 
+/// <param name="Children">Immediate children resolved for the browsed node (this page only).</param>
+/// <param name="Truncated">True when the result was clipped (frame-budget cap or adapter-reported truncation).</param>
+/// <param name="Failure">Structured failure, or null on success.</param>
+/// <param name="ContinuationToken">
+/// Opaque adapter cursor for the NEXT page when more children remain, or null
+/// when this is the final page. Surface it back in a follow-up
+/// <see cref="BrowseNodeCommand.ContinuationToken"/>. Additive (appended last).
+/// </param>
 public record BrowseNodeResult(
     IReadOnlyList<BrowseNode> Children,
     bool Truncated,
-    BrowseFailure? Failure);
+    BrowseFailure? Failure,
+    string? ContinuationToken = null);
 
 public record BrowseFailure(
     BrowseFailureKind Kind,