Align actor add/remove/list/show commands to YAML-first configs,
namespaced names, and --format json|yaml|plain output support.
Changes:
- Add --format option to list, show, add, and update commands
- Add --update flag to add command for updating existing actors
- Add _actor_spec_dict helper for structured output serialization
- Update _print_actor to support format_output rendering
- Add Behave feature tests for CLI format scenarios (11 scenarios)
- Add Robot Framework integration test for show output fields
- Add ASV benchmark for actor CLI parsing overhead
- Add CLI reference documentation for actor commands
ISSUES CLOSED: #288
