Function handle_muxspect_describe 

pub async fn handle_muxspect_describe(
    __arg0: State<AppState>,
    __arg1: Query<MuxspectDescribeQuery>,
) -> impl IntoResponse

GET /api/v1/muxspect/describe?block_id=X — composes ProcessBroker status, the coarse BlockControllerRuntimeStatus, and the OS-process tree for one block into a single response. This is the “describe everything about block X” query REPORT_PROCESS_ARCHITECTURE_STATE_AND_RETHINK_2026_07_22.md §5.4 named as missing — getting this picture today takes 2-3 separate, uncomposed RPC round-trips.