Terrain Add Tree, Add Detail Mesh and Add Grass Texture windows use light Editor theme error icon only and lack help box

Reproduction steps:
1. Create a new project and make sure Editor theme is set to dark
2. Create Terrain GameObject (GameObject > 3D Object > Terrain)
3. Make sure newly created GameObject is selected and click on the “Paint Trees” button in the Inspector Terrain Component
4. Click on the “Edit Trees…” button, select “Add Tree” option and observe the error message in the Add Tree window

Actual result: Light Editor theme error icon is used and error message is not in a help box
Expected result: Dark Editor theme error icon is used and error message is in a help box

Reproducible with: 6000.0.66f1, 6000.3.5f1, 6000.4.0b5, 6000.5.0a5

Reproduced on: Windows 11, macOS Sequoia 26.2 (M4)

Note: Issue is also reproducible with Add Detail Mesh and Add Grass Texture windows