docs(historian): #691 review — breaking change names both SDK defaults (ReturnBounds + IsReadModified), GoodNoData, Gateway horizon, HonorReturnBounds

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

@@ -43,7 +43,8 @@ internal sealed record HistoryEndBound(
 ///         <b>Lookups.</b> "At or before T" is a newest-first read of <c>(0, T]</c> capped at one — native on a backend that
 ///         declares <see cref="IHistorianDataSource.SupportsReverseRaw"/>, otherwise <see cref="ReverseRawReader"/>'s walk-back
 ///         from bounded forward reads (the Gateway: NOT AVEVA's synthetic boundary row, which is stamped at the query start
-///         rather than at the prior sample's own time). "At or after T" is a forward read of <c>[T, MaxValue)</c> capped at one;
+///         rather than at the prior sample's own time). "At or after T" is a forward read of <c>[T, MaxValue)</c> capped at one (on a
+///         forward-only backend ending at now + <see cref="ReverseRawReader.LookAhead"/> instead — #691 review);
 ///         "strictly after T" starts one storage resolution later (lossless: nothing is stored in between). Inside a tie
 ///         cluster the bound is the cluster's first sample in the read's direction — the forward read's first, the reverse
 ///         read's first (the forward order's last).