feat(skills): 添加DDD4j项目构建器技能

- 在marketplace.json中注册新的ddd4j-project-builder技能
- 更新SKILL.md文件标题为DDD4j项目初始化和结构验证
- 使能DDD4j项目构建功能作为新技能模块

.claude-plugin/marketplace.json

@@ -50,6 +50,7 @@
       "skills": [
         "./skills/code-generator",
         "./skills/test-writer",
+        "./skills/ddd4j-project-builder",
         "./skills/documentation-builder",
         "./skills/zh-product-doc-generator",
         "./skills/mcp-builder",

skills/ddd4j-project-builder/SKILL.md

@@ -4,7 +4,7 @@ description: A comprehensive skill for initializing new DDD (Domain-Driven Desig
 license: Complete terms in LICENSE.txt
 ---
 
-# DDD Project Initialization and Structure Validation
+# DDD4j Project Initialization and Structure Validation
 
 ## When to use this skill