Adds a full marketing campaign system to ECC:
- agents/marketing-agent.md — delegatable subagent for campaign planning,
audience research, positioning, copy production, and copy review. Mirrors
the seo-specialist.md structure (frontmatter, prompt defense baseline,
invocation steps, output format, quality bar, hard bans).
- skills/marketing-campaign/SKILL.md — orchestration skill covering the
full campaign workflow: research → positioning → content production →
review. Defines output contract (9 deliverable types) and quality gate.
Delegates upstream to brand-voice, content-engine, crosspost, and
market-research.
- commands/marketing-campaign.md — user-facing /marketing-campaign command
with full, single-deliverable, and copy-review modes. Follows the
commands/ frontmatter convention with description and allowed_tools.