IME composition Enter is not guarded on macOS desktop app

What version of the Codex App are you using (From “About Codex” dialog)?

latest

What subscription do you have?

pro plan 200usd

What platform is your computer?

_No response_

What issue are you seeing?

Issue

On the macOS desktop app, pressing Enter while using an IME composition flow may incorrectly trigger the Enter handler before the composition is finished.

It looks like the desktop version may be missing a guard like:

if (event.isComposing || event.keyCode === 229) {
  return;
}
````

This can cause Enter-to-submit / Enter-to-send behavior to fire while the user is still selecting or confirming composed text, especially for CJK input methods.

### Expected behavior

When the user is composing text with an IME, Enter should not trigger submit/send behavior.

The keydown handler should ignore Enter while composition is active.

### Suggested fix

Add an IME guard before handling Enter:

```js
function onKeyDown(event) {
  if (event.isComposing || event.keyCode === 229) {
    return;
  }

  if (event.key === 'Enter') {
    // existing Enter behavior
  }
}

MDN also documents this pattern for keydown handlers:

https://developer.mozilla.org/en-US/docs/Web/API/Element/keydown_event

Although keyCode is deprecated, MDN notes that keyCode === 229 is still useful for IME cases where isComposing may be false due to event timing. (THIS IS THE ONLY WAY!!!)

What steps can reproduce the bug?

use it normally

What is the expected behavior?

_No response_

Additional information

_No response_