[Jemade]

Initial implementation toward #6416.

• Add string-compatible GEN_AI_OPERATION enum for semantic GenAI operation names.
• Replace a literal operation name in the OpenAI Agents integration.
• Add tests for compatibility and uniqueness.

Draft / validation pending: tests have not yet been executed; enum coverage and existing conventions require maintainer review before this is ready.

[alexander-alderman-webb]

Closing because you've left these in draft for a while.
If you'd like a review feel free to re-open and mark as ready for review.