Auto-delete consumed roughness source after metallic-smoothness repack

PolyHavenMaterialBuilder now removes the separate roughness map (asset +
meta) once its data has been packed into the generated
_metallic_smoothness.png; skipped when the repack fails or roughness came
from the ARM texture.

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

Assets/Scripts/Editor/PolyHaven/PolyHavenMaterialBuilder.cs

@@ -40,6 +40,15 @@ namespace Chameleon.Editor.PolyHaven
             if (!string.IsNullOrEmpty(roughPath) || !string.IsNullOrEmpty(armPath))
                 metallicGlossPath = BuildMetallicSmoothness(folder, slug, roughPath, metalPath, armPath, maxSize);
 
+            // The roughness source is fully consumed into the packed map and never
+            // referenced by the material — drop it once the repack succeeded.
+            if (!string.IsNullOrEmpty(metallicGlossPath) && !string.IsNullOrEmpty(roughPath))
+            {
+                AssetDatabase.DeleteAsset(roughPath);
+                byType.Remove(PolyHavenMapType.Rough);
+                Debug.Log($"[PolyHaven] Deleted consumed roughness source: {roughPath}");
+            }
+
             // AO comes from the dedicated map, or the ARM red channel as a fallback.
             string occlusionPath = null;
             if (byType.TryGetValue(PolyHavenMapType.AO, out var aoSeparate))