Read one owned agent's active native calls across all engine nodes

Reads every configured native engine node for one owned agentId. This is a live snapshot, unlike call history. complete means all engine responses were valid and ownership metadata was complete. outboundCount includes unresolved calls; inboundCount counts callbacks separately. Every outbound row has an opaque nativeRef, startedAt (Unix ms) and resolved. Only verified task calls include callId, taskId, itemId and phoneSha256. A missing mapping remains visible with resolved: false. checkedAt is the ISO snapshot completion time and enginesChecked the node count. Prove no outbound calls only when complete: true, outboundCount: 0 and unresolvedOutboundCount: 0; errors or an incomplete snapshot never prove zero. This endpoint covers native phone calls only, not web sessions or other providers. Uses the existing shared API key rate limit.