[codex] add profile checks workflow

[675401943]

Summary

• add a GitHub Actions workflow for profile README changes
• run the workflow on PRs that touch profile/** or the workflow file itself
• check that the required profile READMEs and image exist
• check that both READMEs keep the Ninifer image reference centered at width="50%"

Validation

• Ran each shell check locally against the current repository contents before committing.
• Verified the PR diff adds only .github/workflows/profile-checks.yml.