Changed deploy-admin build to use sentinel placeholder for asset URLs

[rob-ghost]

Phase 2 of 2: Sentinel-based admin asset URLs

ref https://linear.app/ghost/issue/BER-3300/

Depends on: https://github.com/TryGhost/Ghost-Moya/pull/128 (Phase 1 — must be merged first)

Ghost CI currently builds admin with the production CDN URL hardcoded (https://assets.ghost.io/admin-forward/). Moya downloads this artifact and transforms it into a staging variant by swapping domains using a Node.js script with five npm dependencies. We're changing this so Ghost CI builds with a sentinel placeholder (__GHOST_ASSET_URL__) instead, and Moya replaces it per-environment with a sed one-liner. This decouples the artifact from any specific environment URL.

Full proposal: https://linear.app/ghost/issue/BER-3300/ (see attachment)

This PR (Phase 2 — merge after Phase 1)

Changes the deploy_admin CI job from GHOST_CDN_URL: https://assets.ghost.io/admin-forward/ to GHOST_CDN_URL: __GHOST_ASSET_URL__. The uploaded artifact now contains the sentinel, which Moya's updated workflow (Phase 1) replaces with the correct production or staging URL.

The production Docker image build is unaffected — it omits GHOST_CDN_URL entirely and gets relative paths naturally.

Single-line change.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

🗂️ Base branches to auto review (1)

• 6.x

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

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

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch chore/admin-sentinel-build

---

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 and usage tips.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.81%. Comparing base (6d712ed) to head (d134016).

Additional details and impacted files

@@                        Coverage Diff                        @@
##           feat/production-docker-images   #26393      +/-   ##
=================================================================
- Coverage                          72.82%   72.81%   -0.01%     
=================================================================
  Files                               1561     1561              
  Lines                             120778   120704      -74     
  Branches                           14557    14539      -18     
=================================================================
- Hits                               87956    87893      -63     
+ Misses                             31809    31798      -11     
  Partials                            1013     1013              

Flag	Coverage Δ
admin-tests	52.34% <ø> (-0.02%)	⬇️
e2e-tests	72.81% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.