feat: build procedural lifecycle-safe drive scene

src/scene/world/sun.ts

@@ -0,0 +1,33 @@
+import * as THREE from 'three';
+import type { EnvironmentChapter } from '@/journey/types';
+import type { SceneResourceBag } from '@/scene/resources';
+
+const chapterWarmth: Readonly<Record<EnvironmentChapter, number>> = {
+  'deep-night': 0,
+  systems: 0.12,
+  infrastructure: 0.24,
+  builds: 0.42,
+  'pre-dawn': 0.68,
+  destination: 1,
+};
+
+export function createSun(resources: SceneResourceBag) {
+  const geometry = resources.own('geometry', new THREE.CircleGeometry(18, 64));
+  const material = resources.own('material', new THREE.MeshBasicMaterial({
+    color: 0xff6f83,
+    transparent: true,
+    opacity: 0.82,
+    fog: false,
+  }));
+  const mesh = new THREE.Mesh(geometry, material);
+  mesh.position.set(0, 12, -128);
+
+  return {
+    mesh,
+    update(chapter: EnvironmentChapter, routeProgress: number) {
+      const warmth = Math.max(chapterWarmth[chapter], routeProgress);
+      material.color.setRGB(1, 0.34 + warmth * 0.24, 0.42 + warmth * 0.22);
+      mesh.position.y = 12 + warmth * 5;
+    },
+  };
+}