Use provided sky panorama for skybox integration

tests/Rendering/integration/skybox_scene/Res/skyboxes/source_attribution.txt

@@ -1,11 +1,9 @@
 Skybox source:
-Poly Haven - "farm_field_puresky"
-Page: https://polyhaven.com/a/farm_field_puresky
-Direct download used for preprocessing:
-https://dl.polyhaven.org/file/ph-assets/HDRIs/extra/Tonemapped%20JPG/farm_field_puresky.jpg
+User-provided local sky panorama
 
-License:
-CC0 1.0 Universal (public domain), as provided by Poly Haven.
+Original local file:
+D:\Xuanchi\Main\XCEngine\sky.png
 
 Repository note:
-The file committed here is a resized derivative used only for automated rendering tests.
+The file committed here is the exact sky panorama used by the skybox integration test.
+It is consumed as an equirectangular panorama and converted to a cubemap at runtime.

tests/Rendering/integration/skybox_scene/main.cpp

@@ -404,7 +404,7 @@ void SkyboxSceneTest::BuildScene() {
     camera->SetFarClipPlane(20.0f);
     camera->SetClearColor(XCEngine::Math::Color(0.01f, 0.01f, 0.01f, 1.0f));
     camera->SetSkyboxEnabled(true);
-    Texture* skyboxTexture = CreateCubemapSkyboxTexture(ResolveRuntimePath("Res/skyboxes/farm_field_puresky_1024.jpg"));
+    Texture* skyboxTexture = CreateCubemapSkyboxTexture(ResolveRuntimePath("Res/skyboxes/sky.png"));
     ASSERT_NE(skyboxTexture, nullptr);
     Material* skyboxMaterial = CreateSkyboxMaterial(skyboxTexture);
     ASSERT_NE(skyboxMaterial, nullptr);