Every ceiling this project has hit only appeared under a mixed load, and
three of the four lost work silently while single-feature e2e stayed
green, yet the benchmark only ever ran by hand on one laptop. With
STRESS_REQUIRE_FUNCTIONAL=1 the stress example exits 1 when a download,
upload, search or browse was lost; throughput never fails it because it
measures the machine, not the client. CI now runs a quarter-size profile
against soulfind on every pull request.