feat: Threads should show "Jan using <model_name>" instead of "Assistant"

[dan-jan]

Note: This is a Product discussion, not confirmed as an issue yet.

Objective

• Threads view should educate the user on Jan as an Assistant, but also show the model name
• I would like to propose us have the Assistant reply as "Jan using ", instead of Assistant
• This enables us to push "Jan" as a default Assistant

Screenshots