feat: Enhance comment-based context management system

Major changes:
- ✅ Removed unnecessary documentation files (QUALITY_CHECKLIST, CODING_STANDARDS, EXAMPLES)
- ✅ Enhanced COMMENT_GUIDE.md with comprehensive real-world examples
- ✅ All context now managed through 10 comment tags (5 basic + 5 extended)
- ✅ Updated SETUP_GUIDE.md to emphasize comment-first approach

Key improvements:
- Comment tags now cover: quality standards, performance, security, error handling, testing
- Real production examples for payment processing, authentication, API optimization
- Eliminates need for separate lengthy documentation that AI can't remember
- All context preserved permanently in code via Git

Tag system (10 tags):
Basic (5): inference, decision, todo, context, rule
Extended (5): why, tradeoff, alternative, pattern, reference

Philosophy:
- ❌ Separate docs → AI can't read, docs diverge from code
- ✅ Comment-based → Permanent record, always in sync, searchable

This makes CodeSyncer truly lightweight while maintaining complete context preservation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: bitjaru