[Feat]: Removing agents

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

Working with A2A It seems to be very incontinent that I can't remove agents in the GUI without restating the program, or disabling agents for particular chats.

### Describe the solution you'd like

Removing or disabling agents

### Describe alternatives you've considered

_No response_

### Additional context

Might require to be conversation specific (considering the sysprompt)

### Code of Conduct

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

The issue requests a GUI feature to remove or disable agents without restarting the program. First, examine the repository's structure to locate the GUI code and agent management logic. Look for existing agent lifecycle methods and how they are integrated with the UI. Determine what 'conversation specific' means in the context of the system prompt. A clear definition of 'done' would be a UI control that successfully removes or disables an agent and persists that state.

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