Integration tests (e2e DQN training on 148k bars) take 30+ minutes
in debug mode (opt-level=0). CARGO_PROFILE_TEST_OPT_LEVEL=1 enables
basic optimizations for test binaries — requires recompile but tests
run 5-10x faster. Local dev unaffected (env override only in CI).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>