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/RosterGenerator.cs

@@ -15,17 +15,17 @@ public static class RosterGenerator
         DefCatalog catalog,
         MapLayout map,
         int schoolSeed,
-        string nameSetId,
+        string countryId,
         DateTime? asOf = null,
         string? nativeLanguage = null)
     {
         ArgumentNullException.ThrowIfNull(catalog);
         ArgumentNullException.ThrowIfNull(map);
-        ArgumentException.ThrowIfNullOrWhiteSpace(nameSetId);
+        ArgumentException.ThrowIfNullOrWhiteSpace(countryId);
 
-        if (!catalog.NameSets.TryGetValue(nameSetId, out var names))
+        if (!catalog.TryGetCountryNames(countryId, out var names))
         {
-            throw new ArgumentException($"Unknown name set '{nameSetId}'.", nameof(nameSetId));
+            throw new ArgumentException($"Unknown country '{countryId}'.", nameof(countryId));
         }
 
         var native = NativeLanguages.Pick(names, schoolSeed, nativeLanguage, rollIfOmitted: true);