[WIP] unit tests

[Copilot]

• Analyze existing test patterns in the repository
• Add unit tests for list command (parameter validation, scope logic)
• Add unit tests for use command (parameter parsing, scope selection logic)
• Add unit tests for current command (parameter validation)
• Add unit tests for add command (parameter validation, multi-plugin logic)
• Add unit tests for search command (parameter validation)
• Add unit tests for available command (parameter validation)
• Add unit tests for remove command (parameter validation)
• Add unit tests for update command (parameter validation)
• Add unit tests for config command (parameter validation)
• Run all tests to ensure no regressions
• Review and finalize tests

Original prompt

我这个项目缺少大量的单元测试。 请帮我根据项目实现，补充单元测试。优先完善命令的测试，如果由于实现问题，无法测试，请求修改代码

我这是cli工具，用于管理sdk版本的。

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[aooohan]

@copilot These unit tests of yours are useless; they haven't really reached into the code, for example, when using "use", the logic in the "sdk use" section hasn't been executed.