Function run_watch 

pub async fn run_watch<F, Fut>(
    interval_ms: u64,
    render_fn: F,
    cancel: Option<Receiver<()>>,
) -> Result<()>
where
    F: FnMut() -> Fut,
    Fut: Future<Output = Result<String>>,

Run render_fn in a loop, refreshing the terminal every interval_ms milliseconds. Returns as soon as Ctrl-C is received or the optional cancel channel fires.

Arguments

• interval_ms — refresh interval in milliseconds (clamped to ≥1 ms)
• render_fn — async closure that returns a frame string or an error
• cancel — optional oneshot receiver; when it fires the loop exits