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/performance/budgets.test.ts

@@ -52,6 +52,7 @@ describe('release budgets', () => {
     expect(classifyArtifact('assets/index-a.css', '')).toBe('critical-css');
     expect(classifyArtifact('assets/index-a.js', 'import("./environment-b.js")')).toBe('initial-application-js');
     expect(classifyArtifact('assets/environment-b.js', 'three scene')).toBe('first-live-scene');
+    expect(classifyArtifact('assets/nightdrive-grand-tourer-a.glb', '')).toBe('first-live-scene');
     expect(classifyArtifact('assets/high-tier-b.js', 'optional bloom')).toBe('high-tier-extras');
     expect(() => classifyArtifact('assets/mystery.bin', '')).toThrow(/unclassified/u);
   });