feat: Complete Phase 4 - AI Agents System

- Enhanced agents generator with comprehensive agent definitions
- Added detailed README.md with usage guide and workflow documentation
- Enhanced all 6 agent files (planner, coder, designer, reviewer, tester, devops):
  * Planner: Added numbered folder structure requirements (01-{phase-name}/01-{feature-name}/)
  * Coder: Added design system compliance and implementation guidelines
  * Designer: Added DPR integration and design_rules.mdc compliance
  * Reviewer: Added review checklist and approval workflow
  * Tester: Added Playwright/MCP integration and screenshot capture instructions
  * DevOps: Added RAKD integration and deployment guidelines
- Enhanced workflow.mdc with perfect workflow sequence (Plan → Design → Code → Test → Review → Deploy)
- Enhanced communication.mdc with agent handoff protocols and tagging format
- All agents now enforce strict workflow ordering and communication protocols
- Added screenshot capture requirements for tester agent (.doplan/artifacts/screenshots/)
- Tested and verified all agent files are generated correctly

Author: Test User