Fleet running-agent/model inventory without DM storms

Requirement 6 of KPI-45 (Elazar 2026-08-28): efficient way to inventory which agents/models are currently running across venus/whey/lezama, WITHOUT broadcasting a DM-storm to ask every agent. Likely answer is process-level (ps) + roster + maintainer-registry cross-reference (per OPS-153's method, which worked without any fan-out) rather than asking each agent to self-report. Related: KPI-1 (fleet inventory of scripts, not running processes).