InvocationAck

Acknowledgement returned by the open endpoint — carries the minted
invocation id, fed back into the close call.

id is the generic create-response key (a duplicate of invocation_id), so a
caller's "create X, capture its id" helper reads id from every create-style ack
without knowing the per-command alias. Both surfaces (CLI + MCP) inherit it.

{
    "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
    "invocation_id": "9efe53a2-0f4e-415e-a218-b405e1367798"
}