Remember and use last used model

[atirut-w]

Is your feature request related to a problem? Please describe.
Alpaca seems to be picking a model to use in a chat pretty much randomly. Downloaded a new one? It now prefers another model. Deleted one? Same.

Describe the solution you'd like
When the user pick a model to use, the app should consistently use it across new or all chats until the user pick another.

Describe alternatives you've considered
N/A

Additional context
N/A

[Jeffser]

Hi, every chat picks the last model that sent a message in that particular chat, if the chat is new it picks the first model in the list.

I might add an option to change the model that is selected in new chats but I prefer to leave the behavior of each chat defaulting to the last model used