Replace a campaign's playbook

Replaces the WHOLE playbook with the graph posted. Read the current one first and post it back changed; this does not merge. Shaping a playbook configures what the campaign will send once the owner approves it or their autopilot limits allow it: it approves nothing, sends nothing, and recalls nobody already queued. A graph that could not run answers 422 carrying issues, one per fault, in the validator's stable order. A finished campaign answers 409 (its playbook is the record of what it ran with), and so does an edit that removes a step people are currently standing on. Rate-limited to 60/hour per account, shared with the dashboard's builder. Requires an outreach-scope API key (Pro plan or higher).