tweak static indicator style & behavior (#71128)
Adjusts the styles of the prerender indicator to be smaller, and have it
be expandable rather than always expanded, closer to the original
behavior. This also restores the previous behavior of respecting the
close preference for an hr.
### Before
<details>
<summary>Dark Mode</summary>
</details>
<details>
<summary>Light Mode</summary>
</details>
### After
<details>
<summary>Dark Mode</summary>
https://github.com/user-attachments/assets/a60bafaa-fcf5-4d07-853c-718e12f2b8aa
</details>
<details>
<summary>Light Mode</summary>
https://github.com/user-attachments/assets/ae03eaea-fc4a-4b95-be96-85d7d13b1176
</details>
