Private recall state and complete Responses accumulation

Maintain a strict boundary between canonical Responses state and client output. Every accepted event—including limit-crossing, hidden, recall, reasoning-summary, and provider item_reference lifecycle events—must pass through applyResponsesEvent before filtering or limits; accepted state remains authoritative for postResponse. Never expose response-side item_reference events or terminal forms, recall arguments, Lore user_ids, private errors, or markers through streams or GatewayResponse. Rebuild public output with exact sparse coordinates, cumulative delivery-independent accounting, and valid framing. Roll back before onComplete on every unsuccessful path and keep failure projections public-safe.