Add script-purity tests for name_zh and name_ru

- test_name_zh_no_cyrillic: no Cyrillic in Chinese name field
- test_name_ru_no_foreign_letters: no Latin or CJK in Russian name field

Data fixes: SBH name_ru 'Густав III' (airport) → 'Сен-Бартелемі';
SPR name_ru 'Джона Грейфа II' (airport) → 'Амбергрис-Кей'

test/test_invariants.py

@@ -358,6 +358,20 @@ def test_name_zh_no_latin(dataset):
     assert bad == [], f"name_zh with Latin letters: {bad[:10]}"
 
 
+def test_name_zh_no_cyrillic(dataset):
+    """name_zh must not contain Cyrillic characters."""
+    bad = [(e['code'], e['name_zh']) for e in dataset
+           if e.get('name_zh') and _has_cyrillic(e['name_zh'])]
+    assert bad == [], f"name_zh with Cyrillic: {bad[:10]}"
+
+
+def test_name_ru_no_foreign_letters(dataset):
+    """name_ru must not contain Latin or CJK characters."""
+    bad = [(e['code'], e['name_ru']) for e in dataset
+           if e.get('name_ru') and re.search(r'[A-Za-z]', e['name_ru'])]
+    assert bad == [], f"name_ru with Latin letters: {bad[:10]}"
+
+
 def test_no_double_spaces_in_names(dataset):
     """Name fields must not contain consecutive spaces."""
     bad = []