Activate workflow
USE WHEN: A workflow has been tested via test_and_register_workflow() and is ready to go live. Activate a workflow, enabling its trigger (event-based or scheduled). Archives any previously active trigger and promotes the current DRAFT to the active version. This is the final step in the build flow — the workflow will start running on real events after activation. Always call test_and_register_workflow() first. Activation will fail with 400 if no tested/registered version exists or if the DRAFT fails validation.