Agent-facing "what this is / when to show it" (membership override, else the version description).
Short label for the item's tab (the artifact version's name).
The MJ: Files id to show — streamed securely via the /media route by Media_ShowMedia.
The media kind derived from the artifact version's MIME type.
When true, the agent is told to show this at session start rather than waiting for relevance.
The MJ: Collection Artifacts membership id (stable per kit).
One resolved, model-readable media item in an agent's kit (ordered by its membership
Sequence).