Add workflow to comment on PRs when released

[yugannkt]

Motivation and Context

Adds a workflow that automatically comments on PRs when they're included in a release, notifying contributors their changes are live.

Approach

Custom workflow using GitHub's REST API:

1. Triggers on release published
2. Compares current and previous release tags
3. Extracts PR numbers from commits
4. Validates each is a merged PR (not an issue) via API
5. Comments on each PR: "🎉 This pull request is included in v1.23.3!"

Key Features

Only comments on PRs (not issues) - API validation ensures this
Minimal permissions - only pull-requests: write required

How Has This Been Tested?

Tested with releases v1.23.2 → v1.23.3:

• Successfully found 5 PRs (refactor(auth): remove unused _register_client method #1748, feat: add workflow to comment on PRs when released #1750, Skip empty SSE data to avoid parsing errors #1753, fix: allow MIME type parameters in resource validation (RFC 2045) #1755, chore: remove release-comment workflow #1758)
• Correctly validated all as merged PRs
• Logic verified (commenting failed in fork due to permissions, as expected)

Fixes #1759

Breaking Changes

No, Its an non-breaking change which adds functionality

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[yugannkt]

Ready for your review @maxisbey

[yugannkt]

Ready for your review @felixweinberger

[felixweinberger]

LGTM!

[felixweinberger]

I don't think we need this anymore given we're now using the API only?

[felixweinberger]

Ready for your review @felixweinberger

Thanks! Code LGTM, but curious how you tested this? Did you run this locally somehow to generate the PRs?

[maxisbey]

Will merge this for now and we can validate it works on the next release (will be in Jan)

[Kludex]

If people want to be notified, they can watch the releases... 😅

[yugannkt]

Thanks! Code LGTM, but curious how you tested this? Did you run this locally somehow to generate the PRs?

Hy @maxisbey
I tested this by running the workflow in my fork using GitHub Actions:

1. Pushed the workflow to my fork
2. Modified the trigger temporarily to run on workflow_dispatch (manual trigger)
3. Hardcoded the release tags v1.23.2 → v1.23.3 to simulate a release event
4. The workflow ran against the upstream repo's data (since the commit SHAs and releases are the same)
5. Successfully detected the 5 PRs merged between those releases
6. The actual commenting step failed with a 403 error (as expected) because my fork's GITHUB_TOKEN doesn't have permission to comment on the upstream repo's PRs. But the PR detection logic was fully validated.