feat: add marketing-agent, marketing-campaign skill and command

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.

commands/marketing-campaign.md

@@ -0,0 +1,129 @@
+---
+description: Plan and execute a full marketing campaign. Accepts a product brief and returns positioning, landing page copy, email sequence, social posts, ad variants, video scripts, and a content calendar. Can also review existing copy for conversion quality.
+allowed_tools: ["Read", "Grep", "Glob", "WebSearch", "WebFetch", "Write"]
+---
+
+# /marketing-campaign
+
+Plan and execute a marketing campaign from brief to full content suite.
+
+## Usage
+
+```
+/marketing-campaign                          # Prompt for brief interactively
+/marketing-campaign [product brief]          # Full campaign from inline brief
+/marketing-campaign copy [type]              # Single deliverable only
+/marketing-campaign review [file-or-brief]   # Copy audit for conversion and brand consistency
+```
+
+## What It Does
+
+1. **Research** — Profiles the target audience and maps competitors before writing anything
+2. **Positioning** — Locks the campaign angle and tone profile first
+3. **Copy production** — Generates the full content suite in the right order (landing page → emails → social → ads → video scripts → calendar)
+4. **Review** — Gates all output through a conversion and brand consistency checklist
+
+## Modes
+
+### Full Campaign Mode
+
+Provide a product brief containing:
+- Product name and description
+- Target audience (specific, not generic)
+- Core problem the product solves
+- Core benefit / outcome
+- Tone guidance
+- Channels required
+- Launch goal or timeline
+
+The agent returns all campaign deliverables in order, with a copy review summary at the end.
+
+### Single Deliverable Mode
+
+```
+/marketing-campaign copy landing-page
+/marketing-campaign copy email-sequence
+/marketing-campaign copy social-posts
+/marketing-campaign copy ads
+/marketing-campaign copy video-scripts
+```
+
+Requires positioning to be defined first. Run full mode or provide the angle before requesting a single deliverable.
+
+### Copy Review Mode
+
+```
+/marketing-campaign review path/to/copy.md
+/marketing-campaign review "paste copy here"
+```
+
+Returns a structured audit against:
+- 5-second clarity test (above-fold copy)
+- CTA quality (specific, earned, one per piece)
+- Brand tone consistency
+- Claim specificity and supportability
+- Platform-native fit
+- Cross-channel consistency
+
+## Brief Template
+
+```markdown
+Product: [name]
+Description: [1-3 sentences on what it does]
+Audience: [who, specifically]
+Problem: [the specific pain the product solves]
+Benefit: [the outcome the user gets]
+Tone: [adjectives + what to avoid]
+Channels: [landing page, email, LinkedIn, X, ads, video]
+Goal: [launch, waitlist, signups, awareness — and timeline]
+```
+
+## Output Location
+
+When saving campaign assets, the convention is `.claude/campaigns/{campaign-name}/`:
+
+```
+.claude/campaigns/product-launch/
+├── positioning.md
+├── landing-page.md
+├── email-sequence.md
+├── social-posts.md
+├── ad-copy.md
+├── video-scripts.md
+└── content-calendar.md
+```
+
+Confirm the save location before writing files.
+
+## Examples
+
+```
+/marketing-campaign Build a 7-day launch campaign for an AI career platform for UK university students.
+```
+
+```
+/marketing-campaign copy landing-page
+```
+
+```
+/marketing-campaign review .claude/campaigns/the-key/landing-page.md
+```
+
+## Agent Delegation
+
+This command invokes:
+- `marketing-agent` — campaign planning and copy production
+- `brand-voice` — voice capture when tone needs locking across multiple outputs
+- `content-engine` — platform-native social content production
+- `crosspost` — multi-platform distribution
+- `market-research` — deep audience or competitive intelligence
+
+## Related Commands
+
+- `/plan` — Strategic planning before a campaign
+- `/plan-prd` — Product requirements document before briefing a campaign
+- `/code-review` — Review code behind a landing page implementation
+
+---
+
+*Part of [Everything Claude Code](https://github.com/affaan-m/everything-claude-code)*