createUserRecordType

A user record type carrying the app's own fields.

The built-in {@link ./userRecord.UserRecordType} has the four properties the canvas itself needs. An app that wants people to carry more — a team, a role, a handle to render an avatar from — declares them here rather than stuffing them into meta, so its own code gets them typed.

The record stays in the presence scope: identities are shared with collaborators but never written to a file, because who was in the room is not part of the document.