Add 'use server' directive to markdown renderer

[conico974]

Introduce the 'use server' directive in the contentKit markdown renderer to address potential issues with Next.js incorrectly thinking that the function's is used in a client component.

[changeset-bot]

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Latest commit: d814917

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[linear]

RND-8621 Integration webframe causes published page to throw nextjs 500 error

[github-actions]

Summary of the deployments:

Version	URL	Status
Vercel	https://gitbook-v2-n2wp9jfc8-gitbook.vercel.app	✅
Cloudflare	https://d0a9cab0-gitbook-open-v2-preview.gitbook.workers.dev	✅

Test content

Site	2v	2c
GitBook	https://gitbook-v2-n2wp9jfc8-gitbook.vercel.app/url/gitbook.com/docs	https://d0a9cab0-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.com/docs
E2E	https://gitbook-v2-n2wp9jfc8-gitbook.vercel.app/url/gitbook.gitbook.io/test-gitbook-open	https://d0a9cab0-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	-	Nov 18, 2025, 7:44 PM
v2-cloudflare (Inspect)	👍 Changes approved	3 changed	Nov 18, 2025, 7:49 PM
v2-vercel (Inspect)	👍 Changes approved	4 changed	Nov 18, 2025, 7:48 PM