ESC should close the global search dialog

1. Open a library
2. Search in that library
3. Press Ctrl+Shift+F
4. Global search dialog opens
   <img width="785" height="400" alt="Image" src="https://github.com/user-attachments/assets/171db37e-554b-4470-ba6d-08438b53cca3" />
5. Press Esc
6. Search is cleared (which is correct)
7. Press Esc (again)

Expected: Dialog is closed

Actual: Nothing happens

<img width="793" height="402" alt="Image" src="https://github.com/user-attachments/assets/8db0f56b-d8dd-4ecc-808b-39c0886b807e" />

Note: If clicking somewhere else in the dialog, it closes on Esc.

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A requriement also needs to be added to https://github.com/JabRef/jabref/blob/main/docs/requirements/ux.md - and linked to the implementation.

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Checked 2026-02-16 on Windows, Linux, and macOS.