afs.core: subset keep vert, fix vertical layout

AssFontSubset.Core/src/PyFontTools.cs

@@ -253,13 +253,21 @@ private void ExecuteCmd(ProcessStartInfo startInfo)
     private ProcessStartInfo GetSubsetCmd(SubsetFont ssf)
     {
         var startInfo = GetSimpleCmd(_pyftsubset);
+
+        // GDI doesn’t seem to use any features (may use vert?), and it has its own logic for handling vertical layout.
+        // https://github.com/libass/libass/pull/702
+        // libass seems to be trying to use features like vert/vrt2 to solve this problem.
+        // These are features related to vertical layout but are not enabled: "vchw", "vhal", "vkrn", "vpal", "vrtr". Maybe "vrt2" is also not used.
+        // https://github.com/libass/libass/blob/6e83137cdbaf4006439d526fef902e123129707b/libass/ass_shaper.c#L147
+        string[] enableFeatures = ["vert", "vrt2", "vkna"];
         string[] argus = [
             ssf.OriginalFontFile.FullName,
             $"--text-file={ssf.CharactersFile!}",
             $"--output-file={ssf.SubsetFontFileTemp!}",
             "--name-languages=*",
             $"--font-number={ssf.TrackIndex}",
-            "--no-layout-closure",
+            // "--no-layout-closure",
+            $"--layout-features='{string.Join(',', enableFeatures)}'"
         ];
         foreach (var arg in argus)
         {