feat(skills): add aidd-landing-page skill

[ericelliott]

Summary

Adds a new aidd-landing-page skill that guides agents to build high-converting landing pages using constraint-based programming. The skill encodes ten proven landing page principles as enforceable constraints and provides a structured 5-step workflow.

What's included

Skill file (.cursor/skills/aidd-landing-page/SKILL.md)

• AgentSkills.io-compliant frontmatter with name, description, and compatibility fields
• Role preamble as a conversion-focused front-end engineer and UX strategist
• Capabilities block covering CRO, value proposition design, copywriting, visual hierarchy, performance optimization, A/B test planning, social proof, objection handling, and accessibility
• Constraints block encoding all 10 landing page rules in constraint-based style:
  • One page = one goal
  • 3-second headline clarity test
  • Above-the-fold value prop + CTA
  • Early product screenshots
  • Specific CTA labels
  • Results-driven social proof
  • Clarity over creativity
  • Proactive objection handling
  • Performance targets (Lighthouse ≥ 90, LCP < 2.5s)
  • Single visual hierarchy path
• 5-step workflow: discover → planSections → build → auditSpeed → review
• PageSpeed Insights integration via REST API for automated performance auditing, with Lighthouse CLI fallback for local servers
• 4 commands: /landing-plan, /landing-build, /landing-review, /audit-speed

Task epic (tasks/landing-page-skill-epic.md)

• All requirements in "Given X, should Y" format per aidd-functional-requirements
• Sections: Skill File, Conversion Constraints, Performance Audit, Discover & Plan Workflow, Build Workflow, Review Workflow

Updated files

• plan.md — added Landing Page Skill Epic reference
• AGENTS.md — added landing page => /aidd-landing-page to Task Index