fix: polish pass for traffic, nav, icons, contact email reveal and dashcam robustness

tests/unit/milestones.test.ts

@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'vitest';
 import { SceneResourceBag } from '@/scene/resources';
 import {
+  MILESTONE_FLASH_MAX_RATE,
   createMilestones,
   MILESTONE_FAR_Z,
   MILESTONE_NEAR_Z,
@@ -100,6 +101,24 @@ describe('mile marker mesh', () => {
     resources.dispose();
   });
 
+  it('does not flash posts swept past by a navigator jump or a fling', () => {
+    const resources = new SceneResourceBag();
+    const markers = createMilestones(resources, true);
+    // A navigator long-scroll crosses the whole chapter in about 0.6 s.
+    let peak = 0;
+    for (let frame = 0; frame <= 36; frame += 1) {
+      markers.update('experience', frame / 36, 0, 1 / 60);
+      peak = Math.max(peak, ...markers.flashes());
+    }
+    expect(peak).toBe(0);
+    // Parked, then a single wheel tick at reading pace still flashes the post it crosses.
+    for (let i = 0; i < 90; i += 1) markers.update('experience', passPoint(3, 4) + 0.01, 0, 1 / 60);
+    markers.update('experience', passPoint(3, 4) - 0.01, 0, 1 / 60);
+    expect(markers.flashes()[3]).toBe(1);
+    expect(MILESTONE_FLASH_MAX_RATE).toBeGreaterThan(0.5);
+    resources.dispose();
+  });
+
   it('never flashes on the low tier or touch', () => {
     const resources = new SceneResourceBag();
     const markers = createMilestones(resources, false);