Expand description
Child context operation — isolated subflows.
Implements FR26-FR28: isolated checkpoint namespace, independent operations,
fully owned child contexts sharing only Arc<dyn DurableBackend>.
The child context operation uses OperationType::Context on the wire with
sub_type “Context”. Unlike parallel, there is only a single closure that
runs inline (no tokio::spawn), and the result is returned directly as T
rather than wrapped in BatchResult.