[Feat]: Hopefully there are javascript ui

### Is your feature request related to a problem? Please describe.

Now the ui is mesop with python which is not suitable for commercial companies to transform, adapt, and deploy.

### Describe the solution you'd like

It is hoped that the ui can be replaced with JavaScript so that commercial companies can better adapt to A2A.

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

The issue requests replacing the Python-based Mesop UI with JavaScript for better commercial adaptation. First, examine the current UI implementation in the repository to understand the Mesop integration. Then, research how to build a JavaScript frontend that interfaces with the A2A backend. 'Done' means a new JavaScript UI is proposed or implemented, but the scope is large and undefined.

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