Fix: resolve 404 page asset loading on nested routes

[Bhumikagarggg]

Notes for Reviewers

• This PR fixes the 404 page asset resolution issue for nested missing routes in production (e.g., /foo/bar) by ensuring assets resolve correctly from the appropriate base path.
• The fix preserves relative asset behavior for GitHub Pages PR previews under /pr-preview/pr-<number>/.
• Important: URLs such as /pr-preview/pr-1073/j are currently served by the root GitHub Pages 404.html, not the preview folder’s 404.html. As a result, the exact preview behavior will fully work after the root 404.html is deployed with this redirect logic (post-merge production deploy).
• Tested on nested missing routes and PR preview paths to ensure styling loads correctly.

Screenshot

Signed commits

• Yes, I signed my commits.

[gemini-code-assist]

Code Review

This pull request updates the 404 error page template to support PR previews by dynamically setting the base URL and adding a redirection script. The review feedback highlights a potential issue where a missing trailing slash in the HUGO_PREVIEW_BASE_URL environment variable could cause relative asset URLs to resolve incorrectly, and provides a suggestion to safely append it.

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[github-actions]

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[miacycle]

Duplicate of #1066? @Bhumikagarggg @CodexRaunak

[Bhumikagarggg]

Duplicate of #1066? @Bhumikagarggg @CodexRaunak

hey @miacycle ! Thanks for sharing PR #1066. I checked both approaches.

PR #1066 fixes the issue by injecting a <base> tag through JavaScript inside layouts/partials/head.html only when .Kind == "404". That helps preview assets resolve, but it is a runtime/browser-side workaround and only addresses asset resolution after the 404 page is already loaded.

My PR on fix/404-assest is more complete because it fixes the 404 behavior at the source and workflow level:

• It updates layouts/404.html directly, where the 404 page is actually defined.
• It sets the correct preview base URL during the preview build using HUGO_PREVIEW_BASE_URL.
• It updates the preview workflow URL from GitHub Pages style URL to the actual docs preview URL:
  https://docs.layer5.io/pr-preview/pr-<number>/
• It also redirects nested preview 404 routes to the correct preview 404.html, so assets load correctly even when the missing route is deeply nested.

So PR #1066 mainly fixes asset loading by adding a dynamic base tag in the shared head partial, while my PR handles both parts of the bug:

1. correct asset base path
2. correct nested preview 404 routing

That makes my fix more targeted to the actual 404 page and more reliable for both local and preview deployments.