Update ToC highlighting styles to prevent UI shifts

[HiDeoo]

What kind of changes does this PR include?

• Changes to Starlight code

Description

• Closes ToC highlighting UI shifts #1120

This PR applies the suggested changes from @doodlemarks to prevent UI shifts in the table of contents when scrolling through a page.

Old	New

Currently those styles are also applied on :hover and :focus, but with this update, I think we can remove that and let the default hover/focus styles kick in.

I applied this suggestion too which means that hovering the currently highlighted ToC item will change its color to the default link hover color whereas before hovering the currently highlighted ToC item would have no effect. Just wanted to mention this to make sure this is the intended behavior.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0db5362

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@astrojs/starlight	Minor

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Name	Status	Preview	Updated (UTC)
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[delucis]

Oh nice! This was on my to-do list this week — fun for someone else to do it instead 😁

Left a couple of notes, but the style change looks good to me 🙌

[HiDeoo]

Thanks for the review 🙌 Just applied both suggestions:

• The minor is a good call, UI changes are something I always tend to downplay semver-wise.
• I like the idea of providing the code to keep the old behavior. I would never have thought of that in this case. And thinking more about it, I would not be surprised if some people would prefer the old background color change.

[delucis]

Thanks! This looks great now.

Let’s hold before merging — maybe we can get a few more changes in a new minor. I’d love to review #1175 today and have a few other styling things that could pair well with this.

[delucis]

Although I won’t release the minor just yet, merging this early because I can see a sidebar style issue in #1383 and want to see if it is also present with this change and then fix it once, instead of fixing it for the old styling on that branch and then maybe having to fix again for these changes. Hoping to release v0.16 tomorrow anyway, so hopefully shouldn’t block any other patches between then and now.