[project-42.dev] Restore public GitHub Pages deployment at project-42.dev

[hcs-platform-app]

The canonical public domain project-42.dev is still serving the transitional
project42dev.github.io build. The replacement project42dev/project-42.dev
repository has no GitHub Pages site or deployment workflow, so merged v0.17.0
product changes are not visible at the required public URL.

Restore the approved GitHub Pages production path. OpenAI Sites is not an approved
production host for this domain.

Acceptance criteria:

• The repository builds a static GitHub Pages artifact from governed application source.
• GitHub Actions deploys the exact merged commit through the github-pages environment.
• Cloudflare DNS resolves project-42.dev to GitHub Pages only.
• https://project-42.dev displays the current experience and v0.17.0 release facts.
• Home, learning, resources, profile, learner-data, manifest, sitemap, and representative detail routes pass production checks.
• Rollback and deployment evidence are recorded.

Tracked in Azure DevOps: AB#5690

[hcs-platform-app]

Resolved and production-verified in v0.17.1. PR #61 merged at 86ec453; PR CI 30184671438, main CI 30184798620, and GitHub Pages deployment 30184798618 passed. The canonical domain https://project-42.dev now serves the current site, and critical production routes plus release facts were verified. ADO AB#5690 is Closed/Verified.