Add synthetic keyboard input

Apps can send key chords such as primary+V to whichever app has focus, behind a new keyboard_input permission. The Windows host is written but was not compiled or run locally.

Before

Apps can write the clipboard but cannot paste or press keys in another app.

https://github.com/user-attachments/assets/7d2805e0-7208-48e5-a173-a6cffc12c06f

After

Cmd.keyboard.sendChord posts the chord on macOS and Windows, and Cmd.keyboard.accessStatus checks or requests macOS Accessibility access.

https://github.com/user-attachments/assets/46c19d31-cf21-428c-a48a-7b0199efaa61