End one owned outbound task call with verified native identity

Ends one owned native outbound task call. Send all four expected bindings: expectedAgentId, expectedTaskId, expectedItemId and expectedPhoneSha256 (lowercase SHA-256 of the exact E.164 destination). The server verifies task history, dispatch context, native room, tenant, agent, direction and start time before sending one native hangup. A permanent per-call claim prevents duplicate provider requests, including concurrent requests and timeouts; an Idempotency-Key is unnecessary. The response has callId, outcome and endConfirmed: hung_up means the native engine acknowledged the exact call, already_ended requires a terminal stored call plus absence on all nodes, and unknown never means success. After an unknown result, inspect live activity and stored call state; repeating this endpoint only reads back and never sends another hangup. Recheck active calls after termination. Inbound calls, other tenants, standalone calls and other providers are rejected. Campaign scope, calling windows and deadlines belong to the calling controller; this endpoint does not change billing or task state.