7.3 Create contribution guide with architecture checklist

[Masked-Kunsiquat]

Priority: Low
Estimated Time: 2 hours
Milestone: Optional Enhancements

Problem

No formal checklist for contributors to ensure architecture compliance.

Tasks

• Create or enhance CONTRIBUTING.md
• Add architecture checklist
• Add testing requirements
• Add code review checklist
• Link to ARCHITECTURE.md

Checklist Sections

• Code placement
• Dependencies
• Testing
• Code quality
• Architecture compliance

Success Criteria

• Clear checklist for contributors
• Links to relevant docs
• Used in PR template

See REFACTOR_ROADMAP.md for implementation.