feat: add repayment discounts and interactive net worth trends

Support positive repayment discounts and negative surcharges with exact decimal conversion. Add independent trend toggles, pointer and keyboard date inspection, tests and Chinese documentation.

apps/web/test/net-worth-chart.test.ts

@@ -0,0 +1,45 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { nearestTrendIndex, trendPath, NetWorthChart } from '../src/NetWorthChart';
+import { createElement } from 'react';
+import { renderToStaticMarkup } from 'react-dom/server';
+const rows = [
+  {
+    date: '2026-09-01',
+    assets: '100.86420975',
+    liabilities: '20',
+    net: '80.86420975',
+    complete: true,
+    missing: [],
+  },
+  {
+    date: '2026-09-02',
+    assets: '0',
+    liabilities: '0',
+    net: '0',
+    complete: false,
+    missing: ['USD'],
+  },
+  { date: '2026-09-10', assets: '120', liabilities: '20', net: '100', complete: true, missing: [] },
+];
+test('hover dates use time distance across uneven dates and expose missing dates', () => {
+  assert.equal(nearestTrendIndex(rows, Date.parse('2026-09-02T00:00:00Z')), 1);
+  assert.equal(nearestTrendIndex(rows, Date.parse('2026-09-09T00:00:00Z')), 2);
+  assert.equal(nearestTrendIndex(rows, Date.parse('2026-08-01T00:00:00Z')), 0);
+});
+test('trend paths keep a gap for incomplete dates rather than connecting misleading totals', () => {
+  const path = trendPath(
+    rows,
+    'net',
+    (d) => Number(d.slice(-2)),
+    (v) => Number(v),
+  );
+  assert.equal(path, 'M1,80.86420975  M10,100');
+});
+test('trend legend offers three independent toggles and exact monetary data', () => {
+  const html = renderToStaticMarkup(createElement(NetWorthChart, { rows, base: 'CNY' }));
+  assert.equal((html.match(/aria-pressed="true"/g) || []).length, 3);
+  assert.equal((html.match(/data-series=/g) || []).length, 3);
+  assert.match(html, /80\.86420975/);
+  assert.match(html, /tabindex="0"/);
+});