fix(bot): make tag enforcement check name formatting

PluralKit.Core/Database/Functions/MessageContextExt.cs

@@ -0,0 +1,18 @@
+#nullable enable
+
+namespace PluralKit.Core;
+public static class MessageContextExt
+{
+    public static bool HasProxyableTag(this MessageContext ctx)
+    {
+        var tag = ctx.SystemGuildTag ?? ctx.SystemTag;
+        if (!ctx.TagEnabled || tag == null)
+            return false;
+
+        var format = ctx.NameFormat ?? ProxyMember.DefaultFormat;
+        if (!format.Contains("{tag}"))
+            return false;
+
+        return true;
+    }
+}