🤖🤖🤖 Update quality-playbook skill to v1.4.0 + add agent

[andrewstellman]

Summary

• Updates quality-playbook skill from v1.3.x to v1.4.0
• Adds agents/quality-playbook.agent.md — checks skill installation, explains phases, handles "keep going" / "help" / "what happened"
• Six-phase interactive architecture with end-of-phase messages
• Four iteration strategies (gap, unfiltered, parity, adversarial)
• TDD red-green verification for every confirmed bug
• Quality gate script for mechanical artifact validation
• Moved ITERATION.md into references/ (installed via wildcard copy)

See: https://www.oreilly.com/radar/ai-is-writing-our-code-faster-than-we-can-verify-it/

[github-actions]

🔍 Skill Validator Results

⛔ Findings need attention

Scope	Checked
Skills	1
Agents	1
Total	2
Severity	Count
---	---:
❌ Errors	0
⚠️ Warnings	0
ℹ️ Advisories	0

Summary

Level	Finding
⛔	Only one of --plugin, --skills, or --agents can be used at a time.

Full validator output

```text Only one of --plugin, --skills, or --agents can be used at a time. ```

> **Note:** The validator returned a non-zero exit code. Please review the findings above before merge.

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