Add a chat side bar to control per-conversation settings

[sabaimran]

Chat-level Customization

Generally speaking, it should be easier to determine which model you're chatting with, and to effortlessly update said model from within a given chat.

In this change, we introduce a side bar that allows users to quickly change their chat model, tools, custom instructions, and file filters, directly within the chat view. This removes the need for setting up custom agents for simple instructions and mitigates the requirement to go to the settings page to verify the chat model in action.

The settings page will still configure a per-user default, but the sidebar will allow for greater customization based on the needs of a conversation.

We also extend the chat model to include more attributes that help users make decisions about model selection, including strengths and description. This can help people quickly understand which model might work best for their use case.

Technical Design

We repurpose the backend infrastructure for agents for enabling this functionality. It allows us to integrate conversational adaptation with simplicity. We create hidden agents, which are conversation-specific agents that are not publicly retrievable.

Open Questions

• What should the customization experience look like from the home screen?
  • We don't want to clutter the view of the user on the home screen, so keep it the same. Change the + New button so that it takes you to a more "advanced" new conversation mode, while keeping the current home screen.
• Should image models also be configurable from the side bar?
  • IMO this is probably helpful, but not urgent.

Screenshot