Import Poly Haven materials and scene/authoring updates

Three imported PBR texture sets with generated URP/Lit materials
(Brick 4, Brick Floor 002, Brick Wall 003), scene churn in Main and
The Room, ProBuilder palette/settings updates.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ProjectSettings/Packages/com.unity.probuilder/Settings.json

@@ -199,7 +199,7 @@
             {
                 "type": "UnityEngine.ProBuilder.SelectMode, Unity.ProBuilder, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null",
                 "key": "s_SelectMode",
-                "value": "{\"m_Value\":1}"
+                "value": "{\"m_Value\":4}"
             },
             {
                 "type": "UnityEngine.ProBuilder.ExtrudeMethod, Unity.ProBuilder, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null",