Follow-up of https://github.com/zed-industries/zed/pull/2433
Closes https://github.com/zed-industries/zed/issues/5990

Ensures ESC, Enter and Space buttons are mapped to different buttons on
modals.

Before:

<img width="1728" height="1084" alt="image"
src="https://github.com/user-attachments/assets/7ff63ebf-9396-42a4-9159-e524f974fe2c"
/>


After:

<img width="1728" height="1084" alt="image"
src="https://github.com/user-attachments/assets/634434e7-d907-496b-80c5-b02a69844d63"
/>


Release Notes:

- Improved default button focus in macOS dialogs