Function graceful_shutdown_tree

pub async fn graceful_shutdown_tree<F, Fut>(
    process_manager: &dyn ProcessManager,
    pid: ProcessId,
    send_shutdown: F,
    ack_timeout: Duration,
    exit_timeout: Duration,
) -> Result<GracefulShutdownOutcome, Error>
where
    F: FnOnce() -> Fut + Send,
    Fut: Future<Output = Result<ShutdownTreeResponse, Error>> + Send,

Attempt a graceful shutdown of pid.

The caller provides send_shutdown, which should represent the RPC to the target process’ process.shutdown_tree handler, returning when the target acknowledges the request.

Behavior:

• wait for ack up to ack_timeout
• wait for exit up to exit_timeout
• if either step times out, force-kill the tree and wait again up to exit_timeout

This is intentionally transport-agnostic: IPC wiring lives elsewhere.