PlanRefusalDetails

Every static reason a composition is not executable, in one payload.

A list rather than a single refusal, and that is the whole point. validate returns every
refusal rather than the first "because a caller repairing a plan should see all of it in one
round trip" — a property that exists on the wire only if the transport carries the list.

{
    "refusals": [
        {
            "detail": "string",
            "reason": "unsupported_bound_kind",
            "stage": null
        }
    ]
}