These agents should only be usable as primary session agents, not as
subagent targets via call_omo_agent/task(). Previously MODE was 'all'
which allowed them to be spawned as subagents, leading to confusing
behavior (e.g. Atlas delegating to Hephaestus as a subagent).
Subagent-callable agents remain: oracle, explore, librarian,
multimodal-looker, metis, momus, sisyphus-junior.
Note: Prometheus is not a BuiltinAgentName and is only invoked via
slash commands, so no change needed there.
YeonGyu-Kim
1316a7d8d1