fix(demo): agui demo access return error Failed to parse request: Type definition error: [simple type, class io.agentscope.core.agui.model.MessageContent]

[yytv5]

• 新增MVC消息转换器和WebFlux解码器
• 在自动配置类中注册自定义反序列化组件
• 兼容Spring Boot 4默认Jackson3，仅针对RunAgentInput使用Jackson2
• 新增对应单元测试验证功能正确性

AgentScope-Java Version

[The version of AgentScope-Java you are working on, e.g. 1.0.12, check your pom.xml dependency version or run mvn dependency:tree | grep agentscope-parent:pom(only mac/linux)]

Description

[Please describe the background, purpose, changes made, and how to test this PR]

Checklist

Please check the following items before code is ready to be reviewed.

• Code has been formatted with mvn spotless:apply
• All tests are passing (mvn test)
• Javadoc comments are complete and follow project conventions
• Related documentation has been updated (e.g. links, examples, etc.)
• Code is ready for review

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[yytv5]

fix issue #2703

[codecov]

Codecov Report

❌ Patch coverage is 73.68421% with 5 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ot/agui/mvc/RunAgentInputHttpMessageConverter.java	57.14%	1 Missing and 2 partials ⚠️
...ng/boot/agui/webflux/RunAgentInputJsonDecoder.java	60.00%	0 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!

[AgentScopeJavaBot]

🤖 AI Review

Adds type-scoped Jackson 2 converters for RunAgentInput in both MVC and WebFlux paths, solving Spring Boot 4 / Jackson 3 compatibility. Clean architecture, precise scoping, good tests. Recommendation: APPROVE.

[AgentScopeJavaBot]

🤖 AI Review

Adds type-scoped Jackson 2 converters for RunAgentInput in both MVC and WebFlux paths, solving Spring Boot 4 / Jackson 3 compatibility. Clean architecture, precise scoping, good tests. Recommendation: APPROVE.

[yytv5]

@AgentScopeJavaBot please merge