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>

src/HSchool.People/Seed.cs

@@ -15,6 +15,7 @@ public static class Seed
     public const int CommuteSalt = 7;
     public const int SkillGrantSalt = 8;
     public const int NativeLanguageSalt = 9;
+    public const int ClimatePresetSalt = 10;
 
     /// <summary>A stream that belongs to the school rather than to one family.</summary>
     public static int ForSchool(int schoolSeed, int salt) => Mix(schoolSeed, familyIndex: -1, salt);