feat: daybreak finale turns the contact arrival into a sunrise with a dawn chord

src/scene/world/dawn-light.ts

@@ -0,0 +1,27 @@
+import * as THREE from 'three';
+
+/**
+ * END OF SHIFT: first light. A fixed low sun straight down the road throws a
+ * warm rim on the terrain, the district facades and the asphalt as the dawn
+ * rises. Shared uniform (one set for every generation), like the headlight
+ * beam: the environment writes one float per frame, and 0 skips the term.
+ */
+export const dawnLightUniforms = {
+  uDawnLight: { value: 0 },
+};
+
+/** Toward the sun: low over the horizon, down the road (-z). */
+const SUN_DIRECTION = new THREE.Vector3(0, 0.2, -1).normalize();
+
+/** GLSL: dawnRim(normal, toCamera) -> warm light to add (0 when uDawnLight is 0). */
+export const DAWN_PARS = /* glsl */ `
+  uniform float uDawnLight;
+  vec3 dawnRim(vec3 n, vec3 toCamera) {
+    if (uDawnLight <= 0.0) return vec3(0.0);
+    vec3 sunDir = vec3(${SUN_DIRECTION.x.toFixed(4)}, ${SUN_DIRECTION.y.toFixed(4)}, ${SUN_DIRECTION.z.toFixed(4)});
+    float facing = abs(dot(n, sunDir));
+    float rim = pow(1.0 - abs(dot(n, toCamera)), 2.0);
+    float against = max(0.0, dot(-toCamera, sunDir));
+    return vec3(1.0, 0.6, 0.36) * uDawnLight * (facing * 0.09 + rim * against * 0.24);
+  }
+`;