[FEATURE]: Add initial conformance tests to the a2ui core SDK

The agent SDK currently has platform agnostic conformance tests.

We should add similar conformance tests to the core framework.

Let's start by adding a suite for the data model, e.g. conforming that updateing the data model at different paths etc should work correctly for all edge cases.

This can replace the existing unit tests for the data model in many cases.

1. Research how the framework currently works for the agent SDK
2. Plan how to translate that to the core SDK, including where it should be described in blueprints and readmes etc so that coding agents can discover and manage it. perhaps there should be a skill explaining how our conformance tests work overall. We may want to do some changes to repo structure, e.g. add a /conformance folder with the conformance test definitions and YAML sources of truth
3. Define some tests cases for data model in the core SDK
4. Hook up the conformance tests to the Python and TS data model implementations for now

Please come up with detailed plan for all of this before doing the implementation.

检查 agent SDK 现有的 conformance tests，以了解其结构。规划如何将其调整为适用于 core SDK 的数据模型，同时考虑将定义放置在 /conformance 文件夹中的位置，以及如何与 Python 和 TypeScript 实现集成。这项工作包括在实现之前进行研究、架构规划和测试定义。

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