Four synthetic operator-behaviour scenarios at the merger level
(aggregate_observations) that pin v0's calibration:
* Stable HUMAN over 7 sessions -> all primitives stable
* HUMAN switches to LLM mid-week -> primitives flip stable -> drifting
* Two operators alternating -> primitives flag multi_actor
(per-primitive; the cross-
primitive multi_actor_suspected
correlator is exercised by Phase 5)
* Single short session -> all primitives unknown
Plus a threshold-lockdown test that asserts every named constant in
_thresholds.py against its v0 ship value. Anyone adjusting a
threshold without updating the scenarios fails this file.
This closes DEBT-051 at v0 — the attribution engine has a calibrated,
test-locked answer to "is this attacker stable / drifting / showing
multiple operators?" without crossing the persona-attribution bright
line. v1 (cross-attacker clustering, KD simhash linkage signal) is
gated on this v0 surface being stable in production for >= 1 month.