support-core: split SupportActor into domain userId vs telemetry accountableUserId (VENUS-111 follow-up)

support-core.ts SupportActor={userId,agentLabel} carries ONE id used for BOTH domain author columns (supportTickets.resolvedByUserId L191, supportTicketMessages.authorUserId L296/L386) AND the appEvents actorUserId telemetry stamps (logEvent sites). VENUS-111 normalized every OTHER telemetry actor stamp to accountableActorId (owner under a persona) but left support-core OUT (audit-venus-ca ruling B) because owner-attributing the shared actor.userId would corrupt the domain author columns. FIX: split SupportActor into {userId (domain author, unchanged), accountableUserId (telemetry)}; thread accountableUserId from the session caller (support-actions closeCore/replyCore = accountableActorId(effective)) and the headless bearer route (VENUS-252 support-action API = service-actor id). Only the logEvent actorUserId sites use accountableUserId; DB author writes keep userId. Touches the LOCKED VENUS-252 support-action contract, so it's a deliberate contract change, not a pure refactor.