Add Sequenzy email marketing skill

[polnikale]

Summary

• Adds a sequenzy-email-marketing skill for GitHub Copilot agents.
• Covers safe Sequenzy email-marketing workflows: subscribers, segments, campaigns, sequences, templates, transactional email, API keys, and delivery stats.
• Updates generated skills documentation.

Testing

• git diff --check
• npm ci
• npm run skill:validate
• npm run build

Notes

The canonical installable SKILL.md package remains https://github.com/Sequenzy/skills; this contribution adds a Copilot-native skill entry for this collection.

[github-actions]

🔴 Contributor Reputation Check: HIGH risk

Check	Risk
Profile	HIGH
Credential audit	NONE

Maintainers: please review this contributor before merging.
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[github-actions]

🔍 Skill Validator Results

✅ All checks passed

Scope	Checked
Skills	1
Agents	0
Total	1
Severity	Count
---	---:
❌ Errors	0
⚠️ Warnings	0
ℹ️ Advisories	0

Summary

Level	Finding
ℹ️	Found 1 skill(s)
ℹ️	[sequenzy-email-marketing] 📊 sequenzy-email-marketing: 739 BPE tokens [chars/4: 877] (detailed ✓), 10 sections, 5 code blocks
ℹ️	✅ All checks passed (1 skill(s))

Full validator output

```text Found 1 skill(s) [sequenzy-email-marketing] 📊 sequenzy-email-marketing: 739 BPE tokens [chars/4: 877] (detailed ✓), 10 sections, 5 code blocks ✅ All checks passed (1 skill(s)) ```