feat: validate experimaestro configs in DatasetTests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bpiwowar

src/datamaestro/test/checks.py

@@ -72,4 +72,5 @@ def test_datasets(self):
         """
         for dataset in self.repository:
             with self.subTest(dataset_id=dataset.id):
-                dataset.prepare(download=False)
+                config = dataset.prepare(download=False)
+                config.__xpm__.validate()