UIDebugger attribute fields are read-only in play mode

Steps to reproduce:

1. Create a new project and add a UI Document to the scene with any UXML file.
2. Open Window > UI Toolkit > Debugger and point it at that panel.
3. Select any element in the hierarchy on the left.
4. In the Attributes section on the right, try to change a value such as Name or Tooltip.
5. Enter Play mode and try again.

Actual results:

Almost every field in the Attributes section is greyed out and cannot be changed. Name, Tooltip, View Data Key, Picking Mode, Tab Index, Usage Hints and the text-related values are all read-only. Only a few of them still respond: Pseudo States, Enabled, and the class list.

In Play mode there is a second problem. The Attributes section is emptied and rebuilt from scratch every frame, so it visibly churns while the game is running. Because the field you are typing in is destroyed and replaced sixty times a second, editing an attribute in Play mode would not be possible even if the fields were not greyed out.

Expected results:

The Attributes section lets you change an element's values while you are looking at it, in both Edit mode and Play mode, and keeps the field you are typing in.

Reproducible with versions: trunk (7000.0.0a4)

Not reproducible with versions:

Can't test with versions:

Tested on (OS): Windows 11

Notes:

• The fields that still work are the handful the debugger builds by hand. Everything that was switched over to standard inspector fields is read-only, which is what narrows this down.
• The read-only problem is not limited to Play mode; it happens in Edit mode too. The constant rebuilding is specific to Play mode, because that is when the UI being inspected redraws every frame.