fix(settings): fix nested settings load via environment variables (#1551)

Signed-off-by: Alexander Sokolov <alsokoloff@gmail.com>

tests/test_settings_load.py

@@ -0,0 +1,29 @@
+import os
+
+
+def _setup_env():
+    os.environ["DOCLING_PERF_PAGE_BATCH_SIZE"] = "12"
+    os.environ["DOCLING_DEBUG_VISUALIZE_RAW_LAYOUT"] = "True"
+    os.environ["DOCLING_ARTIFACTS_PATH"] = "/path/to/artifacts"
+
+
+def test_settings():
+    _setup_env()
+
+    import importlib
+
+    import docling.datamodel.settings as m
+
+    # Reinitialize settings module
+    importlib.reload(m)
+
+    # Check top level setting
+    assert str(m.settings.artifacts_path) == "/path/to/artifacts"
+
+    # Check nested set via environment variables
+    assert m.settings.perf.page_batch_size == 12
+    assert m.settings.debug.visualize_raw_layout is True
+
+    # Check nested defaults
+    assert m.settings.perf.doc_batch_size == 2
+    assert m.settings.debug.visualize_ocr is False