Function stream_with 

pub fn stream_with<E>(
    command: &mut Command,
    token: &CancelToken,
    policy: &StreamPolicy,
    consume: impl FnMut(&[u8]) -> Result<(), E>,
) -> Result<StreamOutput, StreamError<E>>

Run one command to completion while its stdout streams through consume. Supervision is identical to capture_with: own process group, cancellation SIGKILLs it, the deadline kills it, stderr is drained concurrently with bounded retention, stdin is /dev/null. Stdout is never retained — a bounded number of chunks is in flight between the reader thread and consume, so memory stays bounded by what the consumer keeps. A consumer error kills the child and surfaces as StreamError::Consumer.