fix: refuse unavailable gallery and pin head trainer

recognization/code/test_engine.py

@@ -274,6 +274,33 @@ class CatalogTests(unittest.TestCase):
         self.assertEqual(product["number_out"], 3)
         self.assertIsNone(engine.update_stock("nope", -1))
 
+
+class GalleryLoadTests(unittest.TestCase):
+    def test_a_failed_gallery_load_returns_none_and_is_not_retried(self):
+        engine, _, _, _ = make_engine(identity_backend="gallery", stock_dir="does-not-exist")
+
+        class BrokenGallery:
+            def __init__(self, *args, **kwargs):
+                pass
+
+            def load(self):
+                raise FileNotFoundError("DINOv2 weights not found")
+
+        import gallery as gallery_module
+
+        original = gallery_module.ProductGallery
+        gallery_module.ProductGallery = BrokenGallery
+        try:
+            self.assertIsNone(engine.identity_gallery())
+            self.assertIsNone(engine.identity_gallery())
+        finally:
+            gallery_module.ProductGallery = original
+            engine.shutdown()
+        self.assertIs(engine._gallery, False)
+
+
+
+class CatalogImageTests(unittest.TestCase):
     def test_catalog_image_path_is_resolved_through_inventory(self):
         engine, _, _, _ = make_engine()
         self.assertIsNone(engine.catalog_image_path("../../etc/passwd"))