GitHub Actions integration — fail CI on low compatibility scores

[Ouranos27]

Problem

Email developers want to catch rendering issues before merge, not after deploy. The engine can score emails, but there's no turnkey CI integration to enforce score thresholds.

Proposal

Create a GitHub Action that:

1. Finds HTML email files (or compiles JSX/MJML) in the repo
2. Runs auditEmail() on each
3. Fails the check if any client score drops below a configurable threshold
4. Posts a PR comment with a score summary table

# .github/workflows/email-check.yml
- uses: emailens/engine-action@v1
  with:
    files: "emails/**/*.html"
    min-score: 70
    clients: "gmail-web,outlook-windows,apple-mail-macos"

PR Comment Output

Email	Gmail	Outlook	Apple Mail
welcome.html	92 ✅	45 ❌	98 ✅
receipt.html	88 ✅	72 ✅	95 ✅

❌ welcome.html scored 45 on Outlook (min: 70). 3 errors: flexbox, gap, box-shadow.

Context

On the roadmap. The @emailens/cli package already exists — the Action could wrap it or use the engine directly.

Acceptance Criteria

• GitHub Action published to marketplace
• Configurable file patterns, client list, and score threshold
• PR comment with score table
• Supports HTML, JSX (React Email), and MJML inputs
• Docs + example workflow