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

tests/unit/daybreak.test.ts

@@ -0,0 +1,79 @@
+import { describe, expect, it } from 'vitest';
+import { DAWN_STEPS, dawnStep, END_OF_SHIFT_SUBLINE } from '@/journey/dawn';
+import {
+  blendDaybreak,
+  CHAPTER_PALETTES,
+  createMutableChapterPalette,
+  DAYBREAK_PALETTE,
+  engineOffStarScale,
+} from '@/scene/world/palette';
+
+describe('dawn step mapping (html[data-dawn])', () => {
+  it('steps night -> first-light -> sunrise -> day at 0.3 / 0.6 / 0.95', () => {
+    expect(DAWN_STEPS).toEqual({ 'first-light': 0.3, sunrise: 0.6, day: 0.95 });
+    const cases: Array<[number, string]> = [
+      [0, 'night'],
+      [0.29, 'night'],
+      [0.3, 'first-light'],
+      [0.59, 'first-light'],
+      [0.6, 'sunrise'],
+      [0.949, 'sunrise'],
+      [0.95, 'day'],
+      [1, 'day'],
+      [-1, 'night'],
+      [Number.NaN, 'night'],
+    ];
+    for (const [dawn, step] of cases) expect(dawnStep(dawn)).toBe(step);
+  });
+
+  it('reads the end-of-shift sub-line', () => {
+    expect(END_OF_SHIFT_SUBLINE).toBe('END OF SHIFT · 05:48');
+  });
+});
+
+describe('daybreak palette', () => {
+  it('is not a journey chapter', () => {
+    expect(Object.keys(CHAPTER_PALETTES)).not.toContain('daybreak');
+  });
+
+  it('leaves the destination untouched at 0 and becomes daybreak at 1', () => {
+    const untouched = createMutableChapterPalette('destination');
+    blendDaybreak(untouched, 0);
+    expect(untouched.sky.getHex()).toBe(CHAPTER_PALETTES.destination.sky);
+    expect(untouched.starVisibility).toBe(CHAPTER_PALETTES.destination.starVisibility);
+
+    const full = createMutableChapterPalette('destination');
+    blendDaybreak(full, 1);
+    for (const key of ['sky', 'fog', 'terrainLow', 'terrainHigh', 'sun', 'haze'] as const) {
+      expect(full[key].getHex()).toBe(DAYBREAK_PALETTE[key]);
+    }
+    expect(full.warmth).toBe(1.25);
+    expect(full.terrainEnergy).toBe(0.4);
+    expect(full.starVisibility).toBe(0);
+    expect(full.streakEnergy).toBe(0);
+  });
+
+  it('blends partway and clamps out-of-range amounts', () => {
+    const half = createMutableChapterPalette('destination');
+    blendDaybreak(half, 0.5);
+    expect(half.warmth).toBeCloseTo((1 + 1.25) / 2);
+    expect(half.starVisibility).toBeCloseTo(0.08);
+    const over = createMutableChapterPalette('destination');
+    blendDaybreak(over, 3);
+    expect(over.sky.getHex()).toBe(DAYBREAK_PALETTE.sky);
+    const nan = createMutableChapterPalette('destination');
+    blendDaybreak(nan, Number.NaN);
+    expect(nan.sky.getHex()).toBe(CHAPTER_PALETTES.destination.sky);
+  });
+
+  it('boosts the stars as the engine cuts, then drains them as the dawn rises', () => {
+    expect(engineOffStarScale(0, 0)).toBe(1);
+    expect(engineOffStarScale(1, 0)).toBeCloseTo(1.8);
+    expect(engineOffStarScale(1, 0.5)).toBeCloseTo(1.4);
+    expect(engineOffStarScale(1, 1)).toBe(1);
+    // Combined with the daybreak blend, the stars are gone by full dawn.
+    const palette = createMutableChapterPalette('destination');
+    blendDaybreak(palette, 1);
+    expect(palette.starVisibility * engineOffStarScale(1, 1)).toBe(0);
+  });
+});