OwnerPrincipalIdField was reading currentClusterAtom, which no callers
ever wrote — so every form submission ended up with
owner_principal_id=null and the backend rejected non-admins with
"Only platform admin can create global ...". Pin the field to
currentOrganizationId instead (the Org the caller is acting under).
Cluster ownership is the wrong source: a cluster_access grant lets one
Org schedule on another Org's cluster, but the new resource is still
owned by the caller's Org, and the backend enforces
owner_principal_id == ctx.current_principal_id.
Also drops the dead currentClusterAtom.
