Storyboard coverage: campaign governance flows

[bokelley]

Add compliance storyboards for campaign governance:

• campaign_governance_denied — over-budget/unauthorized denial flow
• campaign_governance_conditions — conditions applied, re-check flow
• campaign_governance_delivery — delivery monitoring with drift detection

The existing media_buy_governance_escalation.yaml covers the narrative flow but there are no compliance storyboards (with track: campaign_governance) for the denied/conditions/delivery edge cases.

Discovered in #424.

[bokelley]

Done in adcontextprotocol/adcp#1985. Added 3 campaign governance storyboards (campaign_governance_denied, _conditions, _delivery) plus a campaign_governance compliance track with 5 scenarios. All 3 pass against the training agent.