Update empty scene document test and add validation tests for invalid world settings

tests/domain/create-empty-scene-document.test.ts

@@ -9,6 +9,25 @@ describe("createEmptySceneDocument", () => {
 
     expect(document.version).toBe(SCENE_DOCUMENT_VERSION);
     expect(document.name).toBe("Untitled Scene");
+    expect(document.world).toEqual({
+      background: {
+        mode: "solid",
+        colorHex: "#2f3947"
+      },
+      ambientLight: {
+        colorHex: "#f7f1e8",
+        intensity: 1
+      },
+      sunLight: {
+        colorHex: "#fff1d5",
+        intensity: 1.75,
+        direction: {
+          x: -0.6,
+          y: 1,
+          z: 0.35
+        }
+      }
+    });
     expect(document.brushes).toEqual({});
     expect(document.entities).toEqual({});
     expect(document.modelInstances).toEqual({});

tests/domain/scene-document-validation.test.ts

@@ -116,4 +116,38 @@ describe("validateSceneDocument", () => {
       ])
     );
   });
+
+  it("detects invalid world lighting and background settings", () => {
+    const document = createEmptySceneDocument();
+    document.world.background = {
+      mode: "verticalGradient",
+      topColorHex: "sky-blue",
+      bottomColorHex: "#18212b"
+    };
+    document.world.ambientLight.intensity = -0.25;
+    document.world.sunLight.direction = {
+      x: 0,
+      y: 0,
+      z: 0
+    };
+
+    const validation = validateSceneDocument(document);
+
+    expect(validation.errors).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          code: "invalid-world-background-top-color",
+          path: "world.background.topColorHex"
+        }),
+        expect.objectContaining({
+          code: "invalid-world-ambient-intensity",
+          path: "world.ambientLight.intensity"
+        }),
+        expect.objectContaining({
+          code: "invalid-world-sun-direction",
+          path: "world.sunLight.direction"
+        })
+      ])
+    );
+  });
 });