docs: 시스템 아키텍처 및 명령어 문서 추가

- COMMAND.md: 다양한 명령어와 설명 추가
- .claude/commands/design/1-system-architecture: 시스템 아키텍처 관련 문서 삭제
- .claude/commands/sc: 코드 분석, 빌드, 클린업, 설계, 문서화, 추정, 설명, Git 작업, 구현, 개선, 테스트, 문제 해결, 워크플로우 생성 등 다양한 명령어 문서 추가

.claude/commands/sc/improve.md

@@ -0,0 +1,33 @@
+---
+allowed-tools: [Read, Grep, Glob, Edit, MultiEdit, TodoWrite]
+description: "Apply systematic improvements to code quality, performance, and maintainability"
+---
+
+# /sc:improve - Code Improvement
+
+## Purpose
+Apply systematic improvements to code quality, performance, maintainability, and best practices.
+
+## Usage
+```
+/sc:improve [target] [--type quality|performance|maintainability|style] [--safe]
+```
+
+## Arguments
+- `target` - Files, directories, or project to improve
+- `--type` - Improvement type (quality, performance, maintainability, style)
+- `--safe` - Apply only safe, low-risk improvements
+- `--preview` - Show improvements without applying them
+
+## Execution
+1. Analyze code for improvement opportunities
+2. Identify specific improvement patterns and techniques
+3. Create improvement plan with risk assessment
+4. Apply improvements with appropriate validation
+5. Verify improvements and report changes
+
+## Claude Code Integration
+- Uses Read for comprehensive code analysis
+- Leverages MultiEdit for batch improvements
+- Applies TodoWrite for improvement tracking
+- Maintains safety and validation mechanisms