safe_outputs add_comment hard-fails on locked source PR (pr-docs-check recurring failures)

[IEvangelist]

Summary

safe_outputs fails the entire workflow when a comment-target issue/PR is locked.

In microsoft/aspire pr-docs-check workflows (milestone 13.4 analysis), this is currently the dominant deterministic failure signature.

Impact observed

• Signature: safe-outputs-source-pr-locked-comment
• Runs impacted in sample set: 57
• Affected source PRs: 16715

Representative failing runs:

• https://github.com/microsoft/aspire/actions/runs/25377638980
• https://github.com/microsoft/aspire/actions/runs/25376359957
• https://github.com/microsoft/aspire/actions/runs/25376144212
• https://github.com/microsoft/aspire/actions/runs/25375923147
• https://github.com/microsoft/aspire/actions/runs/25375726714
• https://github.com/microsoft/aspire/actions/runs/25375528525
• https://github.com/microsoft/aspire/actions/runs/25375288291
• https://github.com/microsoft/aspire/actions/runs/25375071553

Typical error:
Failed to add comment: Unable to create comment because issue is locked.

Expected behavior

If comment posting fails specifically because the issue/PR is locked, safe_outputs should treat that as non-fatal (warning/skip) and continue processing other outputs, instead of failing the whole job.

Why this matters

For automated agentic workflows, locked source PRs are a valid repo state. Hard-failing on comment emission turns a notification side effect into a release-blocking workflow failure.