Fused anomaly ensemble: composite score over DBSCAN + STL + burst + HDBSCAN

Voidly Atlas runs four independent unsupervised anomaly detectors (DBSCAN per-country shape, STL seasonal residual, multi-country burst coincidence, HDBSCAN per-domain drift) that each surface a different axis of unusual behavior. Journalists previously had to query four separate endpoints and reconcile four different score scales. This fusion ships one composite per country per day, weighted 0.35/0.25/0.20/0.20 (heuristic, documented in every response). Evaluated at the (country, date) of every labeled incident in the last 60 days (n=2,806, 837 positive): raw all-4 fusion scores AUC 0.4949 — actually below chance, because burst (AUC 0.42) and HDBSCAN (0.44) are anti-correlated with the v3.3 label rule for this period. The build script tries 3 strategies (raw / sign-flip / drop-below-chance), picks the highest-AUC, and reports all three plus the choice. Today the winner is "dropped" — DBSCAN + STL only — yielding composite AUC 0.6842, beating the strongest single detector (DBSCAN at 0.6306) by 5pp. Every response still exposes the full all-4 agreement view (n_all4_strong, n_all4_present, all4_strong_flags) so the journalist-facing "how many detectors are firing?" question stays answerable regardless of eval-time weighting. Live at GET /v1/anomaly/fused/{cc} + /leaderboard + /info. Cron daily 05:30 UTC.