Replace selectable name sets with a country that owns names and climate presets.

Create picks a country; climate is rolled from the school seed and stored. Old Slavic saves lift as Russia.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/HSchool.People.Tests/RosterFingerprint.cs

@@ -6,11 +6,11 @@ namespace HSchool.People.Tests;
 /// </summary>
 internal static class RosterFingerprint
 {
-    public static string Format(Roster roster, int seed, string nameSet, string native)
+    public static string Format(Roster roster, int seed, string country, string native)
     {
         var lines = new List<string>
         {
-            $"# seed={seed} nameset={nameSet} native={native} people={roster.People.Count} classes={roster.Classes.Count}",
+            $"# seed={seed} country={country} native={native} people={roster.People.Count} classes={roster.Classes.Count}",
         };
 
         foreach (var schoolClass in roster.Classes.OrderBy(row => row.Id, StringComparer.Ordinal))