Add GitHub Deployments sync for Netlify previews

[dimitrieh]

Description

This PR adds a GitHub Actions workflow that syncs Netlify preview deployments to GitHub's native Deployments API.

The Problem

Netlify does not natively create GitHub Deployment objects when deploying preview builds. While Netlify successfully posts PR comments and status checks, it does not use GitHub's Deployments API. This has been a long-standing limitation that Netlify has consistently declined to implement despite user requests since 2020.

As a result, GitHub's deployment UI shows "This branch has not been deployed" with "No deployments" on pull requests.

How This Works

The workflow is event-driven and automatic:

1. Netlify deploys a preview → posts commit status to GitHub
2. GitHub fires a status event → triggers this workflow
3. Workflow creates a GitHub Deployment object → links to Netlify preview URL
4. GitHub UI updates → shows "Preview" environment with deployment link

No polling, no periodic checks, no wasted Actions minutes. The workflow only runs when Netlify posts a successful preview deployment status.

No Conflicts

This workflow is safe and isolated:

• Per-PR isolation: Each PR gets its own deployment object based on unique commit SHAs
• Multiple PRs: Work independently without interference
• Multiple commits: Old deployments are automatically marked inactive
• Existing workflows: Uses separate status event trigger, doesn't affect other workflows
• Production deployments: Only affects preview deployments (filtered by Netlify context)

Minimal Permissions

The workflow has restricted permissions:

• deployments: write - Only creates deployment metadata
• statuses: read - Only reads Netlify status checks
• contents: read - Only reads repository info

Cannot modify code, push commits, or access secrets.

Related Issue(s)

Resolves the issue where GitHub's deployment UI shows "No deployments" despite Netlify successfully deploying preview builds.

Checklist

• I have read the contribution guidelines
• I have considered the performance impact of these changes
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
• For blog PRs, an Art Request has been created (instructions)

[netlify]

✅ Deploy Preview for flowforge-website ready!

Name	Link
🔨 Latest commit	9c49629
🔍 Latest deploy log	https://app.netlify.com/projects/flowforge-website/deploys/6977666cc60b300007def668
😎 Deploy Preview	https://deploy-preview-4459--flowforge-website.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 81 (🟢 up 24 from production) Accessibility: 80 (no change from production) Best Practices: 100 (🟢 up 8 from production) SEO: 92 (no change from production) PWA: - View the detailed breakdown and full score reports

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To edit notification comments on pull requests, go to your Netlify project configuration.

[dimitrieh]

This PR doesn't yet show a deployment status as GitHub only runs workflows that exist on the main branch, so this workflow won't activate until after it's merged. This is a security measure to prevent malicious code in PRs from executing.

Once merged, all future PRs will automatically get deployment objects when Netlify deploys them. To test it, just create a new PR after merging this one.

[dimitrieh]

@hardillb can you give this a review?

Created this as #4431 is an example where the deployment comment from Netlify is not creating a linear story in the PR. I was confused if it actually deployed the latest changes or not. Also, the having the github deployment status it has not been deployed is not really productive 🙃. This PR should resolve that once merged to master

[hardillb]

@ppawlowski might want to look at this to go with the pre-staging stuff we were talking about in the dev team meeting