[UI] new UI

In preparation for the new event loop, which is to be written decoupled from the visual layer, we need create a UI that is also event driven to take fully leverage the asynchronicity of the new event loop.

This new UI is to live in the crate "chat-cli-ui". As of today, there are the following todos:
- [ ] Input box component (Probably needs subtasks)
- [ ] Chat window component (Probably needs subtasks)
- [ ] Shortcut config

We would probably need to expand on this task as it is being worked on. I am reserving some room for unknown unknowns.

Start by inspecting the chat-cli-ui crate and break the broad task into separate work for the input box, chat window, and shortcut configuration. Clarify the event-driven UI requirements and subtasks before implementation; done should include the agreed components integrated with the new event loop.

Vom Indexierungsmodell aus dem Issue-Text verfasst.