DL-191

The @compass system-sender is a dedicated system account type — a third first-class account shape alongside user and agent (the system = 12 proto case, not an unset-oneof discriminator), startup-seeded and reserved-handle-guarded at account creation, visible only to shared-channel co-members, and structurally never a deliver recipient nor present in directory/roster (no agent_accounts row)

Status: Active (Matt, 2026-08-14)