Fix rendering issues on mobile

[GuillaumeGomez]

Fixes #47723

r? @QuietMisdreavus

[QuietMisdreavus]

This keeps the button from moving into the sidebar menu when it's expanded, but it doesn't help the crate version from sitting underneath it:

[GuillaumeGomez]

Updated.

[QuietMisdreavus]

Now we've gone back to the button being awkward when the menu's open:

(these screenshots taken with firefox's responsive design mode, but it does the same thing in mobile safari on my phone)

[GuillaumeGomez]

I fixed a few others things as well. (Got too much motivation)

[QuietMisdreavus]

We're down to a couple small things that aren't deal-breakers. Let's merge this.

@bors r+ rollup

[bors]

📌 Commit 8a587e6 has been approved by QuietMisdreavus

[QuietMisdreavus]

The things i've found. I'll post an issue once this is merged.

The padding on the top bar seems to be rendered in a different color? It's really subtle in the dark theme, but in the light theme it sticks out. Strangely, when viewing this in Chrome, the color resets to the "proper" one when i start mousing over elements in the inspector (which causes them to be highlighted in the page), so this may be a Chrome thing.

I like how the theme button is next to the search box now, but i guess i expected it to disappear under the menu when it's open? Right now it's just hovering awkwardly over the search box.