ci: add validation for Cloudflare-native deployments

[Teakowa]

Closes #54.

Summary

• replace the GitHub Actions deploy workflow with validation-only CI for pull requests and main
• keep the existing slug-only docs guard, test suite, and Wrangler dry-run build as the CI gate
• remove Cloudflare credentials and Worker deployment from GitHub Actions
• document Cloudflare Workers Builds as the owner of production and branch-preview deployment

Cloudflare setup

Connect the existing workshop-md-converter Worker to wrightkit/workshop-md-converter with Workers Builds, use main as the production branch, and enable builds for non-production branches. Cloudflare will use preview uploads for non-production branches and post build/preview information back to eligible pull requests.

Verification

The PR exercises the new GitHub Actions CI path. The Cloudflare-native deployment path requires the Worker Git integration to be enabled in the Cloudflare dashboard.

[github-actions]

Superseded: this preview was generated by the initial GitHub Actions implementation. PR preview deployments are now intentionally owned by Cloudflare Workers Builds and will be provided by Cloudflare after the Worker Git integration is enabled.

[cloudflare-workers-and-pages]

Deploying with    Cloudflare Workers

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	workshop-md-converter	411a5e9	Commit Preview URL Branch Preview URL	Sep 17 2026, 09:56 AM