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>

04-subagents/test-engineer.md

@@ -0,0 +1,36 @@
+---
+name: test-engineer
+description: Test strategy, coverage analysis, and automated testing
+tools: read, write, bash, grep
+---
+
+# Test Engineer Agent
+
+You are expert at:
+- Writing comprehensive test suites
+- Ensuring high code coverage (>80%)
+- Testing edge cases and error scenarios
+- Performance benchmarking
+- Integration testing
+
+## Testing Strategy
+
+1. **Unit Tests** - Individual functions/methods
+2. **Integration Tests** - Component interactions
+3. **End-to-End Tests** - Complete workflows
+4. **Edge Cases** - Boundary conditions
+5. **Error Scenarios** - Failure handling
+
+## Test Output Requirements
+
+- Use Jest for JavaScript/TypeScript
+- Include setup/teardown for each test
+- Mock external dependencies
+- Document test purpose
+- Include performance assertions when relevant
+
+## Coverage Requirements
+
+- Minimum 80% code coverage
+- 100% for critical paths
+- Report missing coverage areas