test(cowork-service): integration tests for proxy routes — 80 tests passing
Add test files for all 4 new proxy route modules:
- audit/routes.test.ts (5 tests): query, stats, 502 fallback, non-ok forward
- usage/routes.test.ts (5 tests): summary, check-limits, 502 fallback, non-ok forward
- notifications/routes.test.ts (8 tests): prefs get/put, webhooks CRUD, 502 fallback
- extraction/routes.test.ts (5 tests): extract, models, 502 fallback, non-ok forward
All tests use mocked fetch to verify proxy behavior without real services.
80 tests passing (13 test files), typecheck clean.
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