perf: Warm docs manifests and deduplicate builds

[sentry]

This PR addresses an N+1 API call issue occurring on docs pages (/_library/$libraryId/$version/docs/$).

Problem:
When navigating to a docs page, the fetchDocsManifest server function was triggering hundreds of individual HTTP calls to GitHub's content API. This happened because buildDocsManifest (which fetchDocsManifest uses) iterates over every markdown file in a library's docs directory and fetches each one individually to extract frontmatter redirect metadata. While a cache (getCachedDocsArtifact) exists, the GitHub webhook handler (src/routes/api/github/webhook.ts) only marked these artifacts as stale, rather than proactively rebuilding them. Consequently, the first user request after a cache invalidation (or on a cold server start) would incur the full N+1 cost.

Solution:

1. Proactive Cache Warm-up: A new server-only utility, warmDocsArtifacts (src/utils/docs-warm.server.ts), is introduced. After the GitHub webhook handler marks docs artifacts stale, it now calls warmDocsArtifacts in a background task. This rebuilds both the main docs manifest and the docs path manifest immediately, ensuring the cache is warm before subsequent user requests.
2. In-flight Deduplication: buildDocsManifest now includes in-flight deduplication. If multiple concurrent requests attempt to build the same manifest (e.g., during a cold server start), only one build process will execute, and all other pending requests will await and share its result. This prevents redundant GitHub API calls in high-concurrency scenarios.

These changes ensure that docs manifests are always served from a warm cache, significantly reducing the number of outbound GitHub API calls and improving page load performance.

Fixes TANSTACK-COM-4D2

_{This PR was automatically generated by Sentry. You can adjust this setting at any time.}

[coderabbitai]

Important

Review skipped

Bot user detected.

To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: c56292b6-a1aa-462d-82a4-0bebd699e33c

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[cloudflare-workers-and-pages]

Deploying with    Cloudflare Workers

The latest updates on your project. Learn more about integrating Git with Workers.

Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	tanstack-com	d0a64ed	Commit Preview URL Branch Preview URL	Sep 10 2026, 11:16 AM