The referenced co-agent id.
The loaded co-agent's Status, or null when the agent could not be loaded.
The loaded co-agent's TYPE name, or null when missing/unresolvable.
OptionalagentName: stringThe loaded co-agent's display name (for friendlier messages).
The violations (empty array = valid).
PURE invariant core for the co-agent reference (exported for unit tests): the referenced agent must exist, be Active, and be of the Realtime agent type.