Disabled UIToolkit fields can be pasted a value even when disabled

Reproduction steps:

1. Open a project
2. Create a custom Editor window with a text field within a foldout property that is disabled with "foldout.enabledSelf = false;" 
3. Open the custom Editor window and expand the disabled foldout
4. Right-click on the text field and observe the "Paste" option

Actual results: We can paste a value on a disabled UI component using the context menu.

Expected results: The paste entry in the context menu is disabled if the UI component is disabled.

Reproducible with versions: 6000.3.0a1, 6000.6.0a1

Not reproducible with versions: 6000.2.0b2

Tested on (OS): Windows 11, macOS Tahoe 26.3.1 (M4 Max)