UI Builder Project Library foldouts do not open when pressed on the foldout name

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Create a new UI Document Asset (Assets > Create > UI Toolkit > UI Document)
3. Double click the UI Document to open the UI Builder window
4. Open the Project tab in the Library
5. Click on a foldout's name
6. Observe the foldout

Actual results: The foldout does not open

Expected results: The foldout opens

Reproducible with versions: 6000.0.64f1, 6000.2.15f1, 6000.3.2f1, 6000.4.0b1, 6000.5.0a3

Tested on (OS): Windows 11, MacOS Silicon Tahoe 26.0.1

Notes:

• Also reproduces in UI Builder's Hierarchy with added elements