test(ocr): verify load failure does not cache broken entry in SenderModelRegistry

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ocr-service/test_sender_registry.py

@@ -63,3 +63,13 @@ def test_path_outside_models_dir_raises():
     registry = _make_registry()
     with pytest.raises(ValueError, match="not allowed"):
         registry.get_model("/etc/passwd")
+
+
+def test_load_failure_does_not_cache_broken_entry():
+    """A failed load must not leave a broken entry in the cache."""
+    registry = _make_registry()
+    with patch("engines.kraken._load_sender_model", side_effect=RuntimeError("corrupt model")):
+        with pytest.raises(RuntimeError, match="corrupt model"):
+            registry.get_model("/app/models/sender_bad.mlmodel")
+
+    assert registry.size() == 0