ci: add Devin review workflow for blog article PRs

[devin-ai-integration]

Summary

Adds a new GitHub Actions workflow (blog-devin-review.yml) that automatically triggers a Devin session to review blog article PRs. When a PR from a blog/** branch touches files in apps/web/content/articles/, Devin will review the article content and leave inline PR comments with suggestions.

The workflow:

• Triggers on PRs to main from blog/** branches (same pattern as blog-grammar-check.yml)
• Detects changed .mdx article files
• Uses the existing .github/actions/devin composite action to create a Devin session
• Devin is prompted to review for factual accuracy, clarity, structure, missing context, frontmatter completeness, and link validity
• Devin leaves inline PR review comments and a summary comment

Note: The original scope of this PR included modifying blog-auto-format.yml to use the Hyper Charlie bot token, but that workflow was deleted on main by PR #3887, so only the new Devin review workflow remains.

Review & Testing Checklist for Human

• Devin repo access: The workflow creates a Devin session via API with a prompt that instructs Devin to clone the repo and use the GitHub API to leave PR review comments. Verify that Devin sessions created this way have sufficient GitHub access to actually post inline review comments on PRs in fastrepl/hyprnote.
• Review the prompt: Check that the review criteria in the prompt (factual accuracy, clarity, structure, frontmatter, links) match what you actually want reviewed. Add any project-specific style rules or content guidelines that are missing.
• Cost/noise check: Every blog PR on a blog/** branch will spin up a Devin session. Confirm this is acceptable, or consider adding a label-based gate (e.g., only trigger when a review label is added) if you want reviews only on demand.
• End-to-end test: Create a test blog PR on a blog/** branch with an article change → verify the workflow triggers → verify Devin creates a session and leaves review comments on the PR.

Notes

• The DEVIN_API_KEY secret is already configured (used by devin_triage_issues.yaml, devin_update_docs.yaml, etc.)
• Requested by: @ComputelessComputer
• Devin run: https://app.devin.ai/sessions/18892b36f9e94bfaba6927370f929e6a

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[devin-ai-integration]

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 3 additional findings.