Get an organization

Fetches a single organization by organizationId, or by its URL slug when starting from a URL — provide exactly one. The response includes currentMember, the caller’s own membership record with its role (null when the caller has no organization-level membership). Lookups by ID require organization membership; slug lookups additionally work for principals whose only access is a direct website editor grant in the organization, who receive only its ID, name, and URL slug. Inaccessible or deleted organizations return 404.