bug: stacked chat/completions does not work

[louis-jan]

Describe the bug
As a user I would like to send chat/completions requests across threads. Tested with latest Nitro 0.1.32, the second request will yield empty response. I'd like to have it stacked and response a valid response according to my request.

To Reproduce
Steps to reproduce the behavior:

1. Open Nitro 0.1.32
2. Open Jan App and send message to thread A
3. Send message to thread B
4. Thread B shows blank message immediately

Expected behavior
Should have valid message response in thread B after thread A message stream is done

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: MacOS
• Jan Electron latest main
• Nitro 0.1.32

Additional context
Add any other context about the problem here.

[hantran-co]

UX changes:

• When users jump to threads B -> stop LLM streaming for threads A & stream response for threads B instead.
• When users revisit threads A, they will see a copy error (see in design) -> There's a button for users to generate response again.

Design:

Figma link

When users revisit threads A, they will see error:
Whoops! <assistant name>'s generation was interrupted. Let's give it another go!

cc @tikikun @louis-jan