Fix ScrollSectionsList with suspended component

[conico974]

Enhance the ScrollSectionsList component to work correctly with suspended components by integrating a loading state context.

Before this PR and in SSR, suspended elements could be improperly observed.

It also removes <Suspense /> in Block which can decrease the size of the RSC by up to 2Mb in some worst case scenario. (This doesn't have a big impact on user now since most page are ISR/SSG and thus Suspense won't work in these cases)

[linear]

RND-6340 The "On This Page" is not highlighting titles on docs.controlmonkey.io.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 694bae6

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[github-actions]

Summary of the deployments:

Version	URL	Status
Vercel	https://gitbook-v2-5iao2tr8x-gitbook.vercel.app	✅
Cloudflare	https://16897ce4-gitbook-open-v2-preview.gitbook.workers.dev	✅

Test content

Site	2v	2c
GitBook	https://gitbook-v2-5iao2tr8x-gitbook.vercel.app/url/gitbook.com/docs	https://16897ce4-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.com/docs
E2E	https://gitbook-v2-5iao2tr8x-gitbook.vercel.app/url/gitbook.gitbook.io/test-gitbook-open	https://16897ce4-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.gitbook.io/test-gitbook-open

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Build	Status	Details	Updated (UTC)
customers-v2 (Inspect)	✅ No changes detected	-	Jun 26, 2025, 10:42 AM
v2-cloudflare (Inspect)	✅ No changes detected	-	Jun 26, 2025, 10:46 AM
v2-vercel (Inspect)	👍 Changes approved	5 changed	Jun 26, 2025, 10:42 AM