- Added input validation for namespace parameter in _handle_registry_list_tools in src/cleveragents/a2a/facade.py: If provided, must be a non-empty string; empty strings raise ValueError; non-string types raise TypeError
- Added input validation for type_name parameter in _handle_registry_list_resources in src/cleveragents/a2a/facade.py: If provided, must be a non-empty string; empty strings raise ValueError; non-string types raise TypeError
- Added input validation for arguments parameter in _handle_plan_create in src/cleveragents/a2a/facade.py: If provided, must be a dict; non-dict types raise TypeError
- Added input validation for created_by parameter in _handle_plan_create in src/cleveragents/a2a/facade.py: If provided, must be a non-empty string; empty strings raise ValueError; non-string types raise TypeError
- Added BDD feature file features/a2a_facade_optional_param_validation.feature with 17 scenarios covering all validation paths
- Added step definitions features/steps/a2a_facade_optional_param_validation_steps.py
ISSUES CLOSED: #9059
