Add runtime-checkable Protocol typing to all public interfaces.

Enables structural subtyping for consumers while preserving nominal adapter inheritance, instantiation guards, and scan_keys defaults.

Co-authored-by: Cursor <cursoragent@cursor.com>

python_repositories/interfaces/object_repository_interface.py

@@ -1,10 +1,12 @@
-"""Definition of ObjectRepositoryInterface abstract base class."""
+"""Definition of ObjectRepositoryInterface protocol and abstract base class."""
 
-from abc import ABC, abstractmethod
+from abc import abstractmethod
 from io import BytesIO
+from typing import Protocol, runtime_checkable
 
 
-class ObjectRepositoryInterface(ABC):
+@runtime_checkable
+class ObjectRepositoryInterface(Protocol):
     """Interface that defines binary object CRUD methods."""
 
     @abstractmethod