ci: add docs PR checks and trusted preview deploys

[rvagg]

Trying to do two things here:

1. Run in-repo docs validation on every PR, including fork PRs.

• docs-check always runs the markdown lint for docs-relevant changes.
• It also builds the docs when full CI is not already going to do that.
• This gives us GitHub-visible lint/build failures, which the existing Cloudflare preview integration does not provide.

2. Allow manual preview publishing for a reviewed/trusted PR.

• Same-repo branches already get Cloudflare Workers preview URLs from the existing Cloudflare Git integration.
• Fork PRs do not get those previews, and we should not expose Cloudflare secrets to automatic fork PR workflows.
• The manual documentation workflow now accepts a PR number and reviewed commit SHA, checks that the PR head still matches that SHA, restores the trusted Wrangler config from master, then uploads a non-production preview version.

[Copilot]

Pull request overview

Adds a docs-focused CI check for documentation-only pull requests and extends the existing docs publishing workflow to support “trusted” preview deployments by PR number. This fits the repo’s existing Cloudflare/Wrangler-based deploy workflows (similar to demo.yml) while ensuring docs builds happen for docs changes even when full CI wouldn’t otherwise run.

Changes:

• Add pr_number input support to the docs publish workflow to optionally deploy a trusted PR preview (otherwise deploy production from master).
• Introduce a docs-check PR workflow that builds docs when docs-related files change and the full CI workflow is not expected to run.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/docs.yml	Adds optional trusted PR checkout + preview deploy path alongside existing production deploy path.
.github/workflows/docs-check.yml	Adds a PR check to build docs for docs-only changes, skipping when full CI already covers docs builds.

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[BigLep]

Thanks for this. Could you expand the PR description (or a comment in the workflows) on the motivation? In particular the relationship to the existing Cloudflare Workers Builds Git integration: IIUC today that is what builds docs PRs and posts preview URLs (e.g. what I got with #874), but it is configured outside the repo and does not cover fork PRs. Is the intent that we stop relying on that integration, and if so should it be disabled once this lands so we do not run two parallel build pipelines? Having that rationale written down will help the next person understand why both docs-check.yml and the Workers Builds checks exist.

[rvagg]

Updated the original post with more details. What I really want is actual checking / linting of docs on docs PRs, it's extremely annoying when a doc change lands that breaks lint and we end up having to fix it in an unrelated code PR. Plus (the thing that actually triggered this), the ability to see the docs for fork PRs like for #873 - in that case I have no trust issues with the author, I just want to be able to click something to see the preview.