Handle meowstic formes

Closes #1984

PKHeX.Core/Editing/ShowdownSet.cs

@@ -282,9 +282,6 @@ public ShowdownSet(PKM pkm)
             string[] Forms = PKX.GetFormList(Species, types, forms, genderForms, pkm.Format);
             Form = pkm.AltForm > 0 && pkm.AltForm < Forms.Length ? Forms[pkm.AltForm] : string.Empty;
             Format = pkm.Format;
-
-            if (Form == "F")
-                Gender = string.Empty;
         }
         private void ParseFirstLine(string line)
         {

PKHeX.Core/Legality/Checks.cs

@@ -2214,6 +2214,10 @@ bool IsValidPikachuCap()
                         return;
                     }
                     break;
+                case 678: // Meowstic
+                    if (pkm.AltForm != pkm.Gender)
+                        AddLine(Severity.Invalid, V203, CheckIdentifier.Form);
+                    break;
                 case 773: // Silvally
                     {
                         int item = pkm.HeldItem;