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/RosterGeneratorTests.cs

@@ -3,7 +3,7 @@ namespace HSchool.People.Tests;
 public class RosterGeneratorTests
 {
     [Fact]
-    public void SameSeedMapAndNameSet_YieldTheSameRoster()
+    public void SameSeedMapAndCountry_YieldTheSameRoster()
     {
         var map = Fixtures.Classrooms(4);
         var a = Fixtures.Generate(map);