fix(gemini): emit data: [DONE] stream terminator for quick action compatibility

[plon]

Fixes the "add" button not appearing for streaming floating quick action responses.

[suurt8ll]

Thanks! Just out of curiosity, what is this "add" button? I think I've not used or seen it. Can you send a screenshot or a doc page link of it?

[plon]

The "add" button allows you to add the user query and model response pair of a quick action query to the chat. The floating quick action selector appears when you highlight text from the response:

Here, I used the "ask" action and got a response.

What it looks like now, without the "add" button:

What it should look like with the "add" button:

[suurt8ll]

Awesome.