WIP: [codex] Add eval completion webhook support

[Curtis Galione (cjgalione)]

Summary

Adds an eval completion callback and devserver completion webhook support for JavaScript evals.

Changes

• Adds Eval(..., { onComplete }) and calls it once after eval results are produced and logs are flushed.
• Adds on_complete_webhook support to the devserver request schema.
• Adds completion webhook payload construction plus retry/backoff dispatch.
• Adds unit coverage for callback ordering and webhook dispatch behavior.

Validation

Not run locally in this cleanup pass; preserving WIP before machine wipe.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. If this PR is still relevant, please leave a comment, push an update, or remove the stale label. Thank you for your contributions!

[github-actions]

This pull request was closed because it has been inactive for 21 days (14 days of inactivity before being marked stale, plus 7 additional days). If this PR is still relevant, please feel free to reopen it. Thank you!