refactor(rules): eliminate Frontend/Backend duplication with universal coding-standards

**English version:**
- Create docs/rules-en/coding-standards.md with universal coding principles
- Slim down Backend typescript.md to Backend-specific content only
- Slim down Backend typescript-testing.md to Backend-specific content only
- Delete docs/rules-en/ai-development-guide.md (moved to coding-standards.md)
- Slim down Frontend typescript.md to Frontend-specific content only
- Slim down Frontend typescript-testing.md to Frontend-specific content only
- Delete docs/rules-en/frontend/ai-development-guide.md (moved to coding-standards.md)
- Update 8 agent files to reference coding-standards.md instead of ai-development-guide.md

**Japanese version:**
- Apply same refactoring to docs/rules-ja/coding-standards.md
- Migrate common sections from typescript.md to coding-standards.md
- Migrate common sections from typescript-testing.md to coding-standards.md
- Migrate common sections from frontend/typescript.md to coding-standards.md
- Migrate common sections from frontend/typescript-testing.md to coding-standards.md
- Update docs/rules-ja/rules-index.yaml section names to match actual file structure
- Update 7 agents-ja files to reference coding-standards.md instead of ai-development-guide.md

This refactoring implements Approach 4: Linter-like common rules + domain-specific rules
to eliminate 90% duplication between Frontend and Backend documentation.

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

Co-Authored-By: Claude <[email protected]>

Author: shinpr

.claude/agents-en/code-reviewer.md

@@ -11,7 +11,7 @@ Operates in an independent context without CLAUDE.md principles, executing auton
 ## Initial Required Tasks
 
 Load and follow these rule files before starting:
-- @docs/rules/ai-development-guide.md - AI Development Guide, pre-implementation existing code investigation process
+- @docs/rules/coding-standards.md - Universal Coding Standards, pre-implementation existing code investigation process
 - @docs/rules/technical-spec.md - Technical Specifications
 - @docs/rules/typescript.md - TypeScript Development Rules
 - @docs/rules/project-context.md - Project Context
@@ -96,7 +96,7 @@ Load and follow these rule files before starting:
 - [ ] Component dependencies correct
 - [ ] Responsibilities properly separated
 - [ ] Existing codebase analysis section includes similar functionality investigation results
-- [ ] No unnecessary duplicate implementations (Pattern 5 from @docs/rules/ai-development-guide.md)
+- [ ] No unnecessary duplicate implementations (Pattern 5 from @docs/rules/coding-standards.md)
 
 ### Quality Validation
 - [ ] Comprehensive error handling

.claude/agents-en/quality-fixer-frontend.md

@@ -27,10 +27,10 @@ Executes quality checks and provides a state where all checks complete with zero
 ## Initial Required Tasks
 
 Load and follow these rule files before starting:
+- @docs/rules/coding-standards.md - Universal Coding Standards (Anti-patterns, Rule of Three, Debugging, Type Safety)
 - @docs/rules/frontend/typescript.md - Frontend TypeScript Development Rules (React function components, Props-driven design)
 - @docs/rules/frontend/typescript-testing.md - Frontend Testing Rules (React Testing Library, MSW, 60% coverage)
 - @docs/rules/frontend/technical-spec.md - Frontend Quality Check Commands and Build/Test Configuration
-- @docs/rules/frontend/ai-development-guide.md - Frontend Technical Decision Criteria and Anti-patterns
 - @docs/rules/project-context.md - Project Context
 - @docs/rules/architecture/ files (if present)
   - Load project-specific architecture rules when defined

.claude/agents-en/requirement-analyzer.md

@@ -13,7 +13,7 @@ Operates in an independent context without CLAUDE.md principles, executing auton
 Before starting work, be sure to read and follow these rule files:
 - @docs/rules/project-context.md - Project context
 - @docs/rules/technical-spec.md - Technical specifications (refer to documentation process)
-- @docs/rules/ai-development-guide.md - AI development guide (refer to escalation criteria)
+- @docs/rules/coding-standards.md - Universal Coding Standards (refer to escalation criteria and anti-patterns)
 - @docs/rules/documentation-criteria.md - Documentation creation criteria (scale determination and ADR conditions)
 
 ## Responsibilities

.claude/agents-en/task-decomposer.md

@@ -11,7 +11,7 @@ Operates in an independent context without CLAUDE.md principles, executing auton
 ## Initial Mandatory Tasks
 
 Before starting work, be sure to read and follow these rule files:
-- @docs/rules/ai-development-guide.md - Task management principles
+- @docs/rules/coding-standards.md - Universal Coding Standards (task management principles, implementation completeness)
 - @docs/rules/documentation-criteria.md - Documentation creation criteria
 - @docs/rules/typescript-testing.md - TDD process (Red-Green-Refactor)
 - @docs/rules/project-context.md - Generic design guidelines considering future extensions

.claude/agents-en/task-executor-frontend.md

@@ -21,7 +21,7 @@ Load and follow these rule files before starting:
   - Component hierarchy, feature-based structure, etc.
 - **@docs/rules/frontend/typescript.md** - Frontend TypeScript development rules (React function components, Props-driven design, type safety)
 - **@docs/rules/frontend/typescript-testing.md** - Frontend testing rules (React Testing Library, MSW, 60% coverage, Co-location principle)
-- **@docs/rules/frontend/ai-development-guide.md** - Frontend AI development guide, pre-implementation existing code investigation process
+- **@docs/rules/coding-standards.md** - Universal Coding Standards, pre-implementation existing code investigation process
   **Follow**: All rules for implementation, testing, and code quality
   **Exception**: Quality assurance process and commits are out of scope
 

.claude/agents-en/task-executor.md

@@ -21,7 +21,7 @@ Load and follow these rule files before starting:
   - Layered architecture, clean architecture, hexagonal, etc.
 - **@docs/rules/typescript.md** - TypeScript development rules (type definitions, any prohibition, error handling)
 - **@docs/rules/typescript-testing.md** - Testing rules (TDD methodology, test structure, assertion approach)
-- **@docs/rules/ai-development-guide.md** - AI development guide, pre-implementation existing code investigation process
+- **@docs/rules/coding-standards.md** - Universal Coding Standards, pre-implementation existing code investigation process
   **Follow**: All rules for implementation, testing, and code quality
   **Exception**: Quality assurance process (Phase 1-6) and commits are out of scope
 

.claude/agents-en/technical-designer-frontend.md

@@ -14,7 +14,7 @@ Before starting work, be sure to read and follow these rule files:
 - @docs/rules/documentation-criteria.md - Documentation creation criteria
 - @docs/rules/frontend/technical-spec.md - Frontend technical specifications (React, build tool, environment variables)
 - @docs/rules/frontend/typescript.md - Frontend TypeScript development rules (function components, Props-driven design)
-- @docs/rules/frontend/ai-development-guide.md - Frontend AI development guide, pre-implementation existing code investigation process
+- @docs/rules/coding-standards.md - Universal Coding Standards, pre-implementation existing code investigation process
 - @docs/rules/project-context.md - Project context
 - @docs/rules/architecture/implementation-approach.md - Metacognitive strategy selection process (used for implementation approach decisions)
 - @docs/rules/architecture/ architecture rule files (if exist)
@@ -61,7 +61,7 @@ Must be performed before Design Doc creation:
    - List major public Props of target component (about 5 important ones if over 10)
    - Identify usage sites with `Grep: "<ComponentName" --type tsx`
 
-3. **Similar Component Search and Decision** (Pattern 5 prevention from @docs/rules/frontend/ai-development-guide.md)
+3. **Similar Component Search and Decision** (Pattern 5 prevention from @docs/rules/coding-standards.md)
    - Search existing code for keywords related to planned component
    - Look for components with same domain, responsibilities, or UI patterns
    - Decision and action:

.claude/agents-en/technical-designer.md

@@ -14,7 +14,7 @@ Before starting work, be sure to read and follow these rule files:
 - @docs/rules/documentation-criteria.md - Documentation creation criteria
 - @docs/rules/technical-spec.md - Project technical specifications
 - @docs/rules/typescript.md - TypeScript development rules
-- @docs/rules/ai-development-guide.md - AI development guide, pre-implementation existing code investigation process
+- @docs/rules/coding-standards.md - Universal Coding Standards, pre-implementation existing code investigation process
 - @docs/rules/project-context.md - Project context
 - @docs/rules/architecture/implementation-approach.md - Metacognitive strategy selection process (used for implementation approach decisions)
 - @docs/rules/architecture/ architecture rule files (if exist)
@@ -61,7 +61,7 @@ Must be performed before Design Doc creation:
    - List major public methods of target service (about 5 important ones if over 10)
    - Identify call sites with `Grep: "ServiceName\." --type ts`
 
-3. **Similar Functionality Search and Decision** (Pattern 5 prevention from @docs/rules/ai-development-guide.md)
+3. **Similar Functionality Search and Decision** (Pattern 5 prevention from @docs/rules/coding-standards.md)
    - Search existing code for keywords related to planned functionality
    - Look for implementations with same domain, responsibilities, or configuration patterns
    - Decision and action:

.claude/agents-en/work-planner.md

@@ -11,7 +11,7 @@ Operates in an independent context without CLAUDE.md principles, executing auton
 ## Initial Mandatory Tasks
 
 Before starting work, be sure to read and follow these rule files:
-- @docs/rules/ai-development-guide.md - AI development guide, pre-implementation existing code investigation process, task management principles
+- @docs/rules/coding-standards.md - Universal Coding Standards, pre-implementation existing code investigation process, task management principles
 - @docs/rules/documentation-criteria.md - Documentation creation criteria
 - @docs/rules/technical-spec.md - Technical specifications
 - @docs/rules/typescript-testing.md - Testing rules

.claude/agents-ja/code-reviewer.md

@@ -11,7 +11,7 @@ CLAUDE.mdの原則を適用しない独立したコンテキストを持ち、
 ## 初回必須タスク
 
 作業開始前に以下のルールファイルを必ず読み込み、厳守してください：
-- @docs/rules/ai-development-guide.md - AI開発ガイド、実装前の既存コード調査プロセス
+- @docs/rules/coding-standards.md - 普遍的コーディング規約、実装前の既存コード調査プロセス
 - @docs/rules/technical-spec.md - 技術仕様
 - @docs/rules/typescript.md - TypeScript開発ルール
 - @docs/rules/project-context.md - プロジェクトコンテキスト
@@ -96,7 +96,7 @@ CLAUDE.mdの原則を適用しない独立したコンテキストを持ち、
 - [ ] コンポーネント間の依存関係が正しいか
 - [ ] 責務の分離が適切か
 - [ ] 既存コードベース分析セクションに類似機能調査結果が記載されているか
-- [ ] 不必要な重複実装がないか（@docs/rules/ai-development-guide.md パターン5）
+- [ ] 不必要な重複実装がないか（@docs/rules/coding-standards.md パターン5）
 
 ### 品質検証
 - [ ] エラーハンドリングが網羅的か