Spec: draft-campaign output format and approval handoff

[gidutz]

What the campaign-setup agent produces, and how a human approves it before anything ships to the platform.

Output should include:

• The full platform-shaped campaign payload (so it can be submitted as-is on approval)
• A human-readable summary of the choices made
• The brief fields that drove each choice (traceability)
• Items flagged as low-confidence or needing decision
• Estimated cost and pacing if calculable

Approval handoff:

• Where does a human see and approve the draft?
• How are edits captured — do they amend the brief or the draft?
• Audit trail entry created on approve / reject / edit

Deliverable: draft-campaign schema plus approval flow.