Add replace trainer name (Z)

profanity OT/nick => replace with this
not that it is currently being used, as none of the official events have bad OT names, and HOME can't transfer in stuff-yet-to-reset.

PKHeX.Core/PKM/Strings/Trainer/ReplaceTrainerName9a.cs

@@ -0,0 +1,71 @@
+using System;
+
+namespace PKHeX.Core;
+
+/// <summary>
+/// Logic for replacing the name of a Pokémon in <see cref="EntityContext.Gen9a"/>.
+/// </summary>
+public static class ReplaceTrainerName9a
+{
+    /// <summary>
+    /// Checks if the original name is a trigger for replacement, and if the current name is a valid replacement.
+    /// </summary>
+    /// <param name="original">Original name to check for replacement trigger.</param>
+    /// <param name="current">Current name to check for valid replacement.</param>
+    /// <param name="language">Entity language.</param>
+    public static bool IsTriggerAndReplace(ReadOnlySpan<char> original, ReadOnlySpan<char> current, LanguageID language)
+    {
+        if (!IsTrigger(original, language))
+            return false;
+        return IsReplace(current, language);
+    }
+
+    /// <summary>
+    /// Determines whether the specified name should be replaced based on language-specific rules.
+    /// </summary>
+    /// <remarks>This method checks for undefined characters in the name and applies additional rules for
+    /// certain languages. For example, names longer than five characters are flagged for replacement in Asian languages
+    /// such as Japanese, Korean, Simplified Chinese, and Traditional Chinese.</remarks>
+    /// <param name="name">The name to evaluate, represented as a read-only span of characters.</param>
+    /// <param name="language">The language identifier used to apply language-specific rules.</param>
+    /// <returns><see langword="true"/> if the name contains undefined characters or violates language-specific constraints;
+    /// otherwise, <see langword="false"/>.</returns>
+    public static bool IsTrigger(ReadOnlySpan<char> name, LanguageID language)
+    {
+        bool result = !ReplaceTrainerName8.IsValid(name, language);
+        if (result)
+            return true;
+
+        // Skip CheckNgWords: Numbers, whitespace, whitewords, nn::ngc -- implicitly flagged by our WordFilter. No legitimate events trigger this.
+
+        return false; // OK
+    }
+
+    /// <summary>
+    /// Checks if the provided name is one of the valid replacement names for the specified language and game version.
+    /// </summary>
+    /// <param name="name">Current name to check for valid replacement.</param>
+    /// <param name="language">Entity language.</param>
+    public static bool IsReplace(ReadOnlySpan<char> name, LanguageID language)
+    {
+        var expect = GetName(language);
+        return name.SequenceEqual(expect);
+    }
+
+    /// <summary>
+    /// Gets the replacement name for <see cref="EntityContext.Gen9"/> in the given language.
+    /// </summary>
+    public static string GetName(LanguageID language) => language switch
+    {
+        LanguageID.Japanese => "ゼット.",
+        LanguageID.French => "Zed",
+        LanguageID.Italian => "Zeta",
+        LanguageID.German => "Zett",
+        LanguageID.Spanish => "Zeta",
+        LanguageID.SpanishL => "Zeta",
+        LanguageID.Korean => "제트.",
+        LanguageID.ChineseS or LanguageID.ChineseT => "Z.",
+
+        _ => "Z",
+    };
+}