[[PR Description]]

Styles most of the assistant panel. A few notes:

- We now cut off the title if it gets to long so the assistant tools
don't get cut off
- I wasn't able to get to the "no api key" state, so that hasn't been
style checked yet.
- A few of icons were updated in this PR

I also added a new tooltip that teaches you a bit about role cycling:

![CleanShot 2023-12-19 at 12 08
15@2x](https://github.com/zed-industries/zed/assets/1714999/89dcdcc0-9ef9-4527-94a2-6146b5f127f2)

🐜 Known issues 🐜

- There is a bug where zooming the panel makes it shift 1px (@maxdeviant
I think this has to do with panel borders)
- We are showing a timestamp for new conversations before you have sent
a message/launched an assist action. I wasn't sure how to case this out.

Before:

![CleanShot 2023-12-19 at 12 06
17@2x](https://github.com/zed-industries/zed/assets/1714999/16154add-a7f4-455a-a5c5-706847e012a2)

![CleanShot 2023-12-19 at 12 05
00@2x](https://github.com/zed-industries/zed/assets/1714999/a6d325ec-59c2-41b3-ad82-6cf88f2f70a0)

After:

![CleanShot 2023-12-19 at 12 05
37@2x](https://github.com/zed-industries/zed/assets/1714999/aaa4668e-b361-411a-8865-1989bd1c3ae1)

![CleanShot 2023-12-19 at 12 05
52@2x](https://github.com/zed-industries/zed/assets/1714999/0c6a9970-56ab-43cc-9394-fd3f6bf0ed6a)


Release Notes:

- N/A