Keyboard focus and shortcuts not working when opening Help via View Help in Paperback (Shift+F1)

[amirsol81]

I’m running the latest development build of Paperback on Windows 11 25H2. However, this issue has been present in all development versions over the past few days.
If no file is open, when I open Help using the Help → View Help in Paperback (Shift+F1) menu option (or by pressing Shift+F1 directly), Paperback does not place the cursor focus inside the newly opened file. I have to press Tab once to move the focus to the file. But a more serious issue occurs after switching focus to that file: none of the keyboard shortcuts work anymore, for example H, Shift+H, Ctrl+F4, etc. Inside the menus, all shortcuts appear as unavailable (greyed out).

Steps to reproduce:

1. Open Paperback (latest dev build) on Windows 11 25H2, and make sure no file is open.
2. Go to Help → View Help in Paperback or press Shift+F1.
3. Notice that keyboard focus is not automatically placed in the opened file.
4. Press Tab to move focus.
5. Try using shortcuts like H, Shift+H, or Ctrl+F4.
6. Observe that shortcuts do not work and appear unavailable in menus.

Expected behavior:
After opening Help via Shift+F1, the cursor should be placed in the Help file and all keyboard shortcuts should remain functional.

Actual behavior:
Focus is lost, and shortcuts are disabled until restarting or switching views.