Fix CI workflow for format checking

[maniac-en]

Summary

• Updates CI workflow to handle Go formatting via PR comments instead of direct commits to main
• Format check now only runs on pull requests and tags the PR author when formatting is needed
• Removes auto-commit behavior that was conflicting with branch protection rules

Changes

• Format check job now runs only on pull_request events
• Comments on PR with list of unformatted files and tags author
• Main branch pushes only run build/test jobs (no format check since code is pre-validated)

Test Plan

• This PR itself will test the new format check workflow
• Future PRs will use the updated workflow for format validation

[github-actions]

@maniac-en Go code formatting is required. Please run go fmt ./... to format your code and push the changes. Check the action logs for details on which files need formatting.