Function startup_committed_assignment 

pub async fn startup_committed_assignment(
    store: &AssignmentSnapshotStore,
    controller: Option<&ClusterController>,
    head: AssignmentSnapshot,
) -> Result<AssignmentSnapshot, String>

Select the last committed assignment that a cluster process may adopt during startup. A draining head has not transferred ownership, so startup retains its audited predecessor.

Errors

Returns an error when the head or retained predecessor lacks valid durable authority.