Manual interruption

[Sophon]

Unless I missed something in the API reference, the only way to interrupt the current assistant output are:

1. interrupt with the user input
2. disconnect

Our usecase is to stop the conversation. The current solution is to mute or purge the audio data. The problem is that since the assistant output multiple ResponseStarted within one output, there's the edge case:

1. I stop the conversation
2. mute audio
3. Audio data of the current response is discarded
4. Assistant keeps sending responses
5. I want to continue the conversation
6. Assistant is not done yet

One solution is to not accept output until we get ResponseInterrupted:

1. stop conversation
2. mute audio and don't accept transcript
3. user resumes conversation
4. since audio is muted, user doesn't know the assistant is still sending Responses
5. user speaks
6. ResponseInterrupted
7. unmute audio and start accepting Binary

But I think it would be more elegant if there was an event we could send to interrupt the assistant output.