Codex Desktop App (macOS): support Grammarly and other writing assistants in the prompt input

What variant of Codex are you using?

App

What feature would you like to see?

Grammarly and similar writing assistants do not work in the Codex Desktop App prompt/composer input on macOS. The Grammarly Mac desktop app relies on standard macOS accessibility/text APIs to attach to text fields, but the Codex prompt input does not expose itself as a standard editable field, so Grammarly shows no suggestions there at all.

For users who write longer prompts and technical documentation directly in Codex, this means losing grammar, style, and clarity checking that Grammarly provides everywhere else on the system.

Request: make the prompt input compatible with macOS accessibility/text APIs so that Grammarly (and comparable third-party writing tools) can attach and provide spelling, grammar, and style suggestions. An open/standard text field would also benefit other assistive tools, not just Grammarly.

This complements #11846 (native macOS spellcheck), which covers spelling only. This request specifically targets Grammarly/third-party grammar and style checking.

Additional information

Primary use case: composing longer prompts and technical documentation in German and English in the Codex Desktop App, where Grammarly Premium is already used everywhere else on macOS.