Header area in the Multiplayer Center window shrinks when the "Add Gameplay Elements" tab is selected, causing the back arrow button to overlap with UI

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Open the Multiplayer Center window (Window > Multiplayer > Multiplayer Center)
3. Select "Casual co-op" and click the "Select" button
4. Observe the top part of the window with the "Get Started" tab selected (default)
5. Click the "Add Gameplay Elements" tab
6. Observe the top part of the window again

Actual results: The top part of the window (where the "move back" arrow button sits) becomes smaller when the "Add Gameplay Elements" tab is selected, causing the arrow button to overlap with the UI

Expected results: The top part of the window stays the same size regardless of which tab is selected, and the arrow button never overlaps with other UI

Reproducible with versions: 6000.7.0a2, 6000.7.0a3

Not reproducible with versions: 6000.6.0b5, 6000.7.0a1

Can’t test with versions: 6000.0.80f1, 6000.3.20f1, 6000.5.5f1 (due to different window layout)

Tested on (OS): MacOS Silicon Tahoe 26.5.1