fix: Claude token rotation, usage-exhausted fallback, and usage API caching

- Fix token rotation not taking effect: getCurrentToken() was shadowed
  by static .env CLAUDE_CODE_OAUTH_TOKEN value in agent environment
- Don't fall back to Kimi on usage-exhausted (only on transient 429/network)
- Add disk cache for Claude usage API data (survives restarts, 429s)
- Rate-limit usage API calls to 1 per token per 5 minutes
- Add ignoreRateLimits option to rotateToken() for exhausted recovery
- Rotate to next token in getActiveProvider() when current is exhausted
- Add isUsageExhausted() helper to provider-fallback

src/unified-dashboard.test.ts

@@ -0,0 +1,140 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import type { ClaudeAccountUsage } from './claude-usage.js';
+
+vi.mock('./claude-usage.js', () => ({
+  fetchAllClaudeUsage: vi.fn(),
+  fetchAllClaudeProfiles: vi.fn(),
+  getClaudeProfile: (index: number) =>
+    index === 0
+      ? { email: 'a@example.com', planType: 'max' }
+      : { email: 'b@example.com', planType: 'pro' },
+}));
+
+vi.mock('./codex-token-rotation.js', () => ({
+  getAllCodexAccounts: () => [],
+  updateCodexAccountUsage: vi.fn(),
+}));
+
+import {
+  buildClaudeUsageRows,
+  mergeClaudeDashboardAccounts,
+} from './unified-dashboard.js';
+
+describe('unified dashboard Claude usage rows', () => {
+  it('keeps both Claude accounts visible when one account usage is unavailable', () => {
+    const rows = buildClaudeUsageRows([
+      {
+        index: 0,
+        masked: 'tok-a',
+        isActive: true,
+        isRateLimited: false,
+        usage: {
+          five_hour: {
+            utilization: 0.4,
+            resets_at: '2026-03-24T04:00:00+09:00',
+          },
+          seven_day: {
+            utilization: 0.7,
+            resets_at: '2026-03-29T04:00:00+09:00',
+          },
+        },
+      },
+      {
+        index: 1,
+        masked: 'tok-b',
+        isActive: false,
+        isRateLimited: true,
+        usage: null,
+      },
+    ]);
+
+    expect(rows).toHaveLength(2);
+    expect(rows[0]).toMatchObject({
+      name: 'Claude1* max',
+      h5pct: 40,
+      d7pct: 70,
+    });
+    expect(rows[1]).toMatchObject({
+      name: 'Claude2! pro',
+      h5pct: -1,
+      d7pct: -1,
+    });
+  });
+
+  it('preserves the last successful usage per account instead of collapsing to one cache entry', () => {
+    const cachedAccounts: ClaudeAccountUsage[] = [
+      {
+        index: 0,
+        masked: 'tok-a',
+        isActive: false,
+        isRateLimited: false,
+        usage: {
+          five_hour: {
+            utilization: 0.25,
+            resets_at: '2026-03-24T04:00:00+09:00',
+          },
+          seven_day: {
+            utilization: 0.5,
+            resets_at: '2026-03-29T04:00:00+09:00',
+          },
+        },
+      },
+      {
+        index: 1,
+        masked: 'tok-b',
+        isActive: true,
+        isRateLimited: false,
+        usage: {
+          five_hour: {
+            utilization: 0.6,
+            resets_at: '2026-03-24T06:00:00+09:00',
+          },
+          seven_day: {
+            utilization: 0.8,
+            resets_at: '2026-03-30T04:00:00+09:00',
+          },
+        },
+      },
+    ];
+    const liveAccounts: ClaudeAccountUsage[] = [
+      {
+        index: 0,
+        masked: 'tok-a',
+        isActive: true,
+        isRateLimited: false,
+        usage: null,
+      },
+      {
+        index: 1,
+        masked: 'tok-b',
+        isActive: false,
+        isRateLimited: true,
+        usage: {
+          five_hour: {
+            utilization: 0.9,
+            resets_at: '2026-03-24T08:00:00+09:00',
+          },
+          seven_day: {
+            utilization: 0.95,
+            resets_at: '2026-03-31T04:00:00+09:00',
+          },
+        },
+      },
+    ];
+
+    const merged = mergeClaudeDashboardAccounts(liveAccounts, cachedAccounts);
+
+    expect(merged).toHaveLength(2);
+    expect(merged[0]).toMatchObject({
+      index: 0,
+      isActive: true,
+      usage: cachedAccounts[0].usage,
+    });
+    expect(merged[1]).toMatchObject({
+      index: 1,
+      isRateLimited: true,
+      usage: liveAccounts[1].usage,
+    });
+  });
+});