feat(skills): add design-patterns analyzer skill
Comprehensive GoF design patterns analyzer with stack-aware suggestions.
**Features**:
- Detects 23 GoF patterns (Creational, Structural, Behavioral)
- Stack detection (React, Angular, NestJS, Vue, Express, RxJS, Redux, ORMs)
- Code smell detection with pattern suggestions
- Quality evaluation (5 criteria scoring)
- Prefers stack-native alternatives (e.g., React Context over Singleton)
**Structure**:
- 9 files: SKILL.md + reference docs + detection rules + evaluation checklists
- 3 operating modes: Detection, Suggestion, Evaluation
- Pattern-specific documentation for all 23 GoF patterns
**Documentation**:
- Added comprehensive example in guide section 5.4
- Updated examples/README.md with skill entry
- Updated template count: 65 → 66
**Use cases**:
- Analyze existing patterns in codebase
- Suggest refactoring with stack-native patterns
- Evaluate pattern implementation quality
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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