The pipeline runs six stages in order: brief, prompt, generate, filter, upscale, format. The dispatch function takes a brief through each stage by looking up the stage handler in a registry.
Fill in the dispatch line: look up the handler for the current
stage name and call it with the running state dict.
Expected output:
done: {'brief': 'ok', 'prompt': '8/8 knobs', 'generated': 10, 'filtered': 3, 'upscaled': 3, 'formatted': 3}