fix: Add runtime_checkable to Parser protocol

- Add runtime_checkable decorator to Parser protocol
- Add explicit parser marker to shell parser integration test
- Ensure protocol can be used for runtime type checking

Author: dugshub

src/cli_patterns/ui/parser/protocols.py

@@ -54,7 +54,3 @@ def get_suggestions(self, partial: str) -> list[str]:
             List of suggested completions for the partial input
         """
         ...
-
-
-# Explicitly set the runtime checkable attribute for older Python versions
-Parser.__runtime_checkable__ = True

tests/integration/test_shell_parser_integration.py

@@ -23,6 +23,8 @@
 # Import shell and parser components
 from cli_patterns.ui.shell import InteractiveShell
 
+pytestmark = pytest.mark.parser
+
 
 class TestShellParserIntegration:
     """Integration tests for shell and parser system working together."""