test(etl): Wave 4E — real-data e2e + per-route latency regression

[0bserver07]

Summary

Adds two slow-marker test files under a new tests/stackunderflow/integration/ package and registers a slow pytest marker (opt-in via pytest -m slow; default pytest tests/ -q keeps the existing 1474-test collection untouched).

• test_etl_pipeline_e2e.py — builds a 10K-message synthetic store across 5 providers (claude/codex/cursor/gemini/cline) over 30 days × 20 projects, runs every registered Normalizer end-to-end, refreshes every mart, asserts cost conservation across daily/session/project/provider_day/model_day, then sweeps every dashboard route via FastAPI's TestClient asserting 200 + non-empty + <500ms.
• test_route_perf_regression.py — parametrises every dashboard route against a pre-populated marts fixture (100K daily / 50K session / 1K project / 2K provider_day / 5K model_day rows) plus a small 1K-message set so aggregator-driven routes stay tight. Each route runs 1 warmup + 5 cold + 5 warm requests; max(warm) must beat the per-route budget.
• pyproject.toml — new [tool.pytest.ini_options] section registers the slow marker and adds addopts = "-m 'not slow'" so the default suite skips the slow tests automatically. Run the new suite with pytest -m slow.

/api/etl/status is listed for forward compatibility — the route isn't implemented yet on main, so the test accepts a 404 (e2e) / pytest.skip (regression) until the endpoint lands.

Latency table (dev box, M-series, Python 3.12)

route                                cold(p50)  warm(p50)  warm(max)  budget
/api/projects?include_stats=true        5.8ms      5.8ms      6.2ms    100ms
/api/dashboard-data                     8.6ms      7.1ms      7.7ms    100ms
/api/cost-data?period=month            12.1ms     11.9ms     16.0ms    100ms
/api/cost-data/by-provider              1.4ms      1.1ms      2.6ms     50ms
/api/compare?period=month               1.7ms      1.7ms      1.8ms    100ms
/api/yield?period=week                  1.3ms      1.2ms      1.2ms    200ms
/api/optimize?period=month             81.9ms    100.7ms    153.2ms    200ms
/api/messages/summary                   1.8ms      1.6ms      1.6ms     50ms
/api/etl/status                                              (404 — route not yet implemented)

Test counts

• Default pytest tests/ -q → 1472 passed, 2 skipped, 11 deselected (slow tests). Total collection 1474 — matches baseline.
• pytest -m slow tests/stackunderflow/integration -q → 10 passed, 1 skipped (the /api/etl/status placeholder).

Test plan

• pytest -m slow tests/stackunderflow/integration -q — 10 passed + 1 skipped (etl_status placeholder).
• pytest tests/ -q — 1472 passed + 2 skipped + 11 deselected (unchanged from baseline).
• ruff check tests/stackunderflow/integration/ — all checks passed.
• No source code touched (Wave 4E scope discipline) — only test files + pyproject.toml marker config + CHANGELOG.

🤖 Generated with Claude Code