[Feat]: Support multi-turn conversation

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

Some interactions are multi-turn. For example the remote agent could require more information (`input-required` state). It would be nice to support this by allowing to reuse the same task id (if available).

### Describe the solution you'd like

Add a checkbox "reply" (reserve task id) next to the message textbox / "Send" button.

In case there is a task identifier (the `taskId` field should likely be populated):

* The checkbox is enabled
* If selected, the message that is sent will include the `taskId` of the previous message

This will allow testing multi-turn interactions.

### Describe alternatives you've considered

It is possible to use a script with custom code that does that but it would be giving up on the niceties of a2a-inspector.

One can "hack it" though the developer console, setting a break-point and manually modifying the sent message but this ugly.

### Additional context

_No response_

### Code of Conduct

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

Look at the UI component for the message textbox and send button, likely in a file like src/components/ChatInterface.tsx or similar. Understand how taskId is passed and stored in the application state. The change involves adding a checkbox, conditionally enabling it based on taskId presence, and modifying the message-sending logic to include the previous taskId when the checkbox is selected. Check existing tests for the chat interface to see how to test the new feature.

Escrito por el modelo de indexación a partir del texto del issue.