Fall back from invalid settings stores (#1416)

tests/test_settings_store_shape.py

@@ -0,0 +1,20 @@
+from src import settings
+
+
+def test_load_settings_falls_back_for_non_object_json(tmp_path, monkeypatch):
+    settings_file = tmp_path / "settings.json"
+    settings_file.write_text("[]", encoding="utf-8")
+    monkeypatch.setattr(settings, "SETTINGS_FILE", str(settings_file))
+    settings._invalidate_caches()
+
+    assert settings.load_settings() == settings.DEFAULT_SETTINGS
+    assert settings.is_setting_overridden("default_model") is False
+
+
+def test_load_features_falls_back_for_non_object_json(tmp_path, monkeypatch):
+    features_file = tmp_path / "features.json"
+    features_file.write_text("[]", encoding="utf-8")
+    monkeypatch.setattr(settings, "FEATURES_FILE", str(features_file))
+    settings._invalidate_caches()
+
+    assert settings.load_features() == settings.DEFAULT_FEATURES