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>

01-slash-commands/README.md

@@ -404,10 +404,10 @@ Access with: `/deploy/production`, `/test/unit`, `/docs/api`
 
 ## Related Concepts
 
-- **[Subagents](../02-subagents/)** - For complex, delegated tasks
-- **[Memory](../03-memory/)** - For persistent context
-- **[Skills](../05-skills/)** - For auto-invoked capabilities
-- **[Plugins](../06-plugins/)** - For bundled command collections
+- **[Memory](../02-memory/)** - For persistent context
+- **[Skills](../03-skills/)** - For auto-invoked capabilities
+- **[Subagents](../04-subagents/)** - For complex, delegated tasks
+- **[Plugins](../07-plugins/)** - For bundled command collections
 
 ## Resources