GitHub Copilot grok-4.5 is routed to Chat Completions during model generation

[jay-tau]

Summary

GitHub Copilot grok-4.5 is still classified as openai-completions during model generation, but Copilot exposes this model through the Responses API. Requests then fail with:

400 model "grok-4.5" is not accessible via the /chat/completions endpoint

Current behavior

• The live models.dev catalog includes active github-copilot/grok-4.5.
• packages/ai/scripts/generate-models.ts sends only gpt-5* and oswe* Copilot models to openai-responses.
• packages/ai runs model generation as part of its build, so a build against the current catalog generates grok-4.5 with api: "openai-completions".
• The checked-in generated catalog currently omits Copilot Grok, which hides the failure until regeneration.

Expected behavior

Map the exact GitHub Copilot model ID grok-4.5 to openai-responses.

Related: #875 (original report), #906 (validated fix), and #611 (regeneration output).

I already have a focused fix and regression test validated in #906. I'm happy to rebase/update it and submit the fix if a maintainer would like me to.