feat: refine nightdrive world and authored car

Integrate the Blender grand tourer with a cohesive shader-driven road, terrain, atmosphere, lighting, and post-processing pass. Refine responsive drive dynamics and sign lifecycle behavior, and add durable visual, accessibility, and performance verification evidence.

tests/unit/scene-resources.test.ts

@@ -157,31 +157,31 @@ describe('scene render quality', () => {
 
     expect(high).toEqual({
       pixelRatio: 1.5,
-      roadSegments: 192,
-      terrainSegments: 96,
+      roadSegments: 224,
+      terrainSegments: 112,
       terrainOctaves: 3,
-      starCount: 384,
-      streakCount: 48,
+      starCount: 760,
+      streakCount: 112,
       postScale: 1,
       postEffects: true,
     });
     expect(medium).toEqual({
       pixelRatio: 1.5,
-      roadSegments: 144,
-      terrainSegments: 64,
+      roadSegments: 168,
+      terrainSegments: 80,
       terrainOctaves: 2,
-      starCount: 192,
-      streakCount: 28,
+      starCount: 420,
+      streakCount: 64,
       postScale: 0.7,
       postEffects: true,
     });
     expect(low).toEqual({
       pixelRatio: 1.25,
-      roadSegments: 96,
-      terrainSegments: 32,
+      roadSegments: 112,
+      terrainSegments: 48,
       terrainOctaves: 1,
-      starCount: 64,
-      streakCount: 12,
+      starCount: 160,
+      streakCount: 28,
       postScale: 0,
       postEffects: false,
     });