fix(opcua): reverse HistoryRead-Raw paging no longer stops after the first page

A reverse read (start > end) with a small NumValuesPerNode resumed through
the tie-cluster path, which drained the cluster and stepped FORWARD to
T + 1 tick - outside a reverse window - so the read ended with GoodNoData
after one sample. SliceTieCluster now steps down to T - 1 tick for a
reverse read (terminal at the excluded end), and the node manager slices
the over-fetched cluster in the read's own direction so the skip count is
not applied from the wrong end. Forward paging is unchanged.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/HistoryPaging.cs

@@ -205,14 +205,29 @@ internal static class HistoryPaging
     ///     remains, or <c>null</c> when the window is exhausted (terminal — no continuation point).</param>
     /// <param name="nextSkip">The next page's boundary skip count: the running emitted-tie total while the
     ///     cluster drains, else <c>0</c> after advancing past it.</param>
+    /// <param name="reverse">
+    ///     <c>true</c> for a reverse read (Part 11: <c>start &gt; end</c>, samples in descending time, window
+    ///     <c>(end, start]</c>). A drained cluster then steps DOWN to <c>T − 1 tick</c>, which is lossless for the
+    ///     same reason <c>T + 1 tick</c> is going forward, and the read continues only while that is still strictly
+    ///     after <paramref name="endUtc"/> (the reverse window excludes <c>end</c>; a resume at exactly <c>end</c>
+    ///     would turn into a <c>start == end</c> point read and return the excluded sample). Forward is unchanged.
+    /// </param>
     public static void SliceTieCluster(
         int clusterCount, int skip, uint cap, DateTime boundaryT, DateTime endUtc,
-        out int sliceStart, out int sliceCount, out DateTime? nextStartUtc, out int nextSkip)
+        out int sliceStart, out int sliceCount, out DateTime? nextStartUtc, out int nextSkip,
+        bool reverse = false)
     {
         sliceStart = Math.Min(skip, clusterCount);
         sliceCount = Math.Min((int)cap, clusterCount - sliceStart);
         var emitted = sliceStart + sliceCount;
         if (emitted < clusterCount) { nextStartUtc = boundaryT; nextSkip = emitted; }
+        else if (reverse)
+        {
+            // DateTime.MinValue cannot step down; nothing can lie below it anyway.
+            var more = boundaryT > DateTime.MinValue && boundaryT.AddTicks(-1) > endUtc;
+            nextStartUtc = more ? boundaryT.AddTicks(-1) : null;
+            nextSkip = 0;
+        }
         else
         {
             var next = boundaryT.AddTicks(1);