Function play_script 

pub fn play_script(yaml: &str) -> Result<(), String>

Replay a dayscript against the running app, in-process (docs/dayscript.md “Recording”): parse yaml and run each step through the embedded engine, on the main thread between flushes — the same executor day launch --script drives. Returns an error while a recording is live (a replay must not record itself) and on web (no background thread — drive the page over the WebSocket transport there). See record.