Improve metrics clarity, exploration, and refresh reliability

tests/unit/ui-metrics.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it } from 'vitest';
+import { compareMetricValues, metricDuration, metricNumber, metricPercent } from '../../src/lib/ui/metrics.js';
+
+describe('metric presentation', () => {
+    it('distinguishes unavailable evidence, zero, and tiny nonzero values', () => {
+        expect(metricPercent(0, 0)).toBe('—');
+        expect(metricPercent(0, 1)).toBe('0.0%');
+        expect(metricPercent(0.0001, 1)).toBe('<0.1%');
+        expect(metricDuration(0)).toBe('0 h');
+        expect(metricDuration(0.1 / 3600)).toBe('<1 s');
+        expect(metricDuration(45 / 3600)).toBe('45 s');
+        expect(metricDuration(90 / 3600)).toBe('1.5 min');
+        expect(metricNumber(0.0125)).toBe('<0.1');
+    });
+
+    it('sorts numerically while putting unavailable observations last in both directions', () => {
+        const values = [2, null, 100, 0, 10];
+        expect([...values].sort((a, b) => compareMetricValues(a, b, 'desc'))).toEqual([100, 10, 2, 0, null]);
+        expect([...values].sort((a, b) => compareMetricValues(a, b, 'asc'))).toEqual([0, 2, 10, 100, null]);
+    });
+});