Function spawn_worker_with_spool 

pub fn spawn_worker_with_spool(
    capacity: usize,
    bridge: Arc<dyn EventBus>,
    embedder: Arc<dyn Embedder>,
    vector_sink: Arc<dyn VectorSink>,
    spool_dir: Option<PathBuf>,
    metrics: Arc<Registry>,
) -> WorkerHandle

Start the worker pool with vector persistence and optional ATIF journal.