FIX: Enable Netlify preview deployments for Dependabot PRs

[mmcky]

Summary

This PR migrates Netlify preview deployment from custom implementation to the shared quantecon/actions/preview-netlify@v0.6.0 action maintained in the quantecon/actions repository.

Motivation

1. Enable Dependabot previews: The original motivation was to enable Netlify preview deployments for Dependabot PRs (like ⬆️ Bump quantecon-book-theme from 0.15.1 to 0.16.0 #800) to inspect visual/theme changes before merging.

2. Reduce code duplication: The custom implementation duplicated ~260 lines of deployment logic that's now centralized across all QuantEcon lecture repositories.

3. Improve maintainability: The shared action is tested and maintained in one place, making updates and bug fixes easier.

Changes

Replaced ~260 lines of custom code with shared action:

- name: Preview Deploy to Netlify
  uses: quantecon/actions/preview-netlify@v0.6.0
  with:
    netlify-auth-token: ${{ secrets.NETLIFY_AUTH_TOKEN }}
    netlify-site-id: ${{ secrets.NETLIFY_SITE_ID }}
    build-dir: _build/html

Features Preserved

The shared action provides identical functionality:

• ✅ Automatic Netlify deployment with predictable PR URLs
• ✅ Changed lecture file detection
• ✅ Smart PR comments with direct links to modified pages
• ✅ Duplicate comment prevention
• ✅ Built-in security handling (automatically skips forks/Dependabot when secrets unavailable)

Setup Required

Dependabot secrets are configured at the organization level to enable previews for Dependabot PRs:

Organization secrets configured at https://github.com/organizations/QuantEcon/settings/secrets/dependabot:

• ✅ NETLIFY_AUTH_TOKEN (Dependabot-specific token)
• ✅ NETLIFY_SITE_ID (same as Actions secrets)

With these configured, Dependabot PRs will automatically get Netlify preview deployments.

Security

The shared action handles security properly:

• Same repository PRs (including Dependabot with secrets) → Deploy with preview
• Fork PRs → Skip deployment (can't access secrets)

Benefits

1. Enables Dependabot previews - The original goal is achieved ✅
2. Version stability - Using v0.6.0 tag that Dependabot can auto-update
3. Maintainability - Centralized updates across all QuantEcon lecture repos
4. Code reduction - 98% less code (-257 lines) in this repository

[github-actions]

📖 Netlify Preview Ready!

Preview URL: https://pr-804--sunny-cactus-210e3e.netlify.app (935df28)

[Copilot]

Pull request overview

This PR migrates the repository’s Netlify preview deployment logic in CI from an inlined custom implementation to the shared quantecon/actions/preview-netlify@v0.6.0 action, with the stated goal of enabling preview deployments for Dependabot PRs and reducing workflow maintenance burden.

Changes:

• Replaced the custom Netlify deploy + changed-file detection + PR commenting logic with quantecon/actions/preview-netlify@v0.6.0.
• Removed explicit Netlify secrets from job-level env and now passes them as action inputs.

[mmcky]

Copilot Feedback Addressed

Thanks for the review! I've addressed both issues:

✅ Issue 1: Workflow Permissions

Added explicit permissions to the workflow in commit d57db31:

permissions:
  contents: read
  pull-requests: write

This ensures the preview-netlify action can post PR comments even in repositories with restricted default GITHUB_TOKEN permissions.

✅ Issue 2: Dependabot Secrets

The Dependabot secrets concern is already resolved. We've configured organization-level Dependabot secrets:

• NETLIFY_AUTH_TOKEN (Dependabot-specific token)
• NETLIFY_SITE_ID

These are available at: https://github.com/organizations/QuantEcon/settings/secrets/dependabot

With this configuration, Dependabot PRs using the pull_request trigger do have access to secrets and will successfully deploy Netlify previews.

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The PR is now ready with both Copilot recommendations implemented! 🎉

[mmcky]

@jstac I am starting to see some joy in +7/-263 merges. Hooray for code reduction :-)

[github-actions]

📖 Netlify Preview Ready!

Preview URL: https://pr-804--sunny-cactus-210e3e.netlify.app

Commit: ab970d1

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Build Info

• Workflow: Build Project [using jupyter-book]