refactor: Reorganize repository structure for optimal learning path

Reorder folders based on learning dependencies, complexity, and frequency of use:
- 01-slash-commands (unchanged) - Quick wins for beginners
- 02-memory (was 03) - Essential foundation
- 03-skills (was 05) - Auto-invoked capabilities
- 04-subagents (was 02) - Task delegation
- 05-mcp (was 04) - External integration
- 06-hooks (was 07) - Event automation
- 07-plugins (was 06) - Bundled solutions
- 08-checkpoints (unchanged) - Safe experimentation
- 09-advanced-features (unchanged) - Power user tools

Documentation improvements:
- Add LEARNING-ROADMAP.md with detailed milestones and exercises
- Simplify README.md for better scannability
- Consolidate Quick Start and Getting Started sections
- Combine Feature Comparison and Use Case Matrix tables
- Reorder README sections: Learning Path → Quick Reference → Getting Started
- Update all cross-references across module READMEs

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

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

08-checkpoints/README.md

@@ -461,12 +461,11 @@ Use both together:
 
 ## Related Concepts
 
-- **[Planning Mode](../07-planning/)** - Create detailed implementation plans before coding
-- **[Memory Management](../06-memory/)** - Managing conversation history and context
-- **[Code Navigation](../05-code-navigation/)** - Understanding and navigating your codebase
-- **[Real-time Collaboration](../09-collaboration/)** - Working with teams using Claude Code
-- **[Error Handling](../10-error-handling/)** - Handling and recovering from errors
-- **[Best Practices](../11-best-practices/)** - General best practices for Claude Code usage
+- **[Advanced Features](../09-advanced-features/)** - Planning mode and other advanced capabilities
+- **[Memory Management](../02-memory/)** - Managing conversation history and context
+- **[Slash Commands](../01-slash-commands/)** - User-invoked shortcuts
+- **[Hooks](../06-hooks/)** - Event-driven automation
+- **[Plugins](../07-plugins/)** - Bundled extension packages
 
 ## Summary