feat: add the nav bar's lower-bezel wave canvas

A lazy chunk (journey/nav-wave.ts) that draws the bar's wave: a calm
ribbon at cruise, a spectrum at speed, with a hue cycle near the top of
the dial. It follows the chapter's accent and the dawn, repaints at once
on resize, and draws one still frame under reduced motion. Budgeted as a
deferred chunk.

tests/performance/budgets.test.ts

@@ -74,6 +74,7 @@ describe('release budgets', () => {
     expect(classifyArtifact('assets/DashcamFrame-c.css', '.dashcam-frame{}')).toBe('deferred-non-video');
     expect(classifyArtifact('assets/tab-icon-c.js', 'renderTabIcon')).toBe('deferred-non-video');
     expect(classifyArtifact('assets/speedometer-dial-c.js', 'createSpeedometerDial')).toBe('deferred-non-video');
+    expect(classifyArtifact('assets/nav-wave-c.js', 'mountNavWave')).toBe('deferred-non-video');
     expect(() => classifyArtifact('assets/mystery.bin', '')).toThrow(/unclassified/u);
   });