feat(web): show Codex plan usage in header

test/plan-usage-latest.test.ts

@@ -0,0 +1,18 @@
+/** @fileoverview Merging Claude status-line usage with polled Codex usage. */
+
+import { expect, it } from 'vitest';
+import * as latestModule from '../src/web/plan-usage-latest.js';
+
+it('preserves the Codex row when a later Claude status-line sample arrives', () => {
+  const module = latestModule as Record<string, unknown>;
+  expect(module.setLatestCodexPlanUsage).toBeTypeOf('function');
+  const setCodex = module.setLatestCodexPlanUsage as (value: unknown) => unknown;
+  const setClaude = module.setLatestPlanUsage as (value: Record<string, unknown>) => unknown;
+
+  setCodex({ sevenDay: { usedPercentage: 40, resetAt: 3000 } });
+  expect(setClaude({ sessionId: 's1', fiveHour: { usedPercentage: 97, resetAt: 1000 } })).toEqual({
+    sessionId: 's1',
+    fiveHour: { usedPercentage: 97, resetAt: 1000 },
+    codex: { sevenDay: { usedPercentage: 40, resetAt: 3000 } },
+  });
+});