8 swimmers isn't a test, it's a demo — match test scale to production scale

Testing with half the data of your real use case doesn't test your real use case. Here, the wave allocator expects 2 full waves of 8 — but the test database had 8 swimmers total, meaning wave splitting never triggered. The fix: scale mock data to the actual production scenario, not just 'enough to click around.' Doubling from 8 to 16 made the second wave path exercised for the first time.