assistant2: Refine empty states design (#27812)

| No LLM provider | Fresh Start | No ToS |
|--------|--------|--------|
| ![CleanShot 2025-03-31 at 7  04
17@2x](https://github.com/user-attachments/assets/aab5987c-1530-401d-acc6-65e4f2fc13b8)
| ![CleanShot 2025-03-31 at 7  04
39@2x](https://github.com/user-attachments/assets/b2c7a2e0-5178-4bcb-a917-da7bf8e6246c)
| ![CleanShot 2025-03-31 at 7  05
10@2x](https://github.com/user-attachments/assets/4a656e82-0e1d-4d11-8d34-8eeeadd4814c)
|

Release Notes:

- N/A
dce824f095Danilo Leal committed on 3/31/2025, 10:31:56 PM· committed by GitHubparenta1bef28
2 files changedLine totals unavailable