Function spawn_status_emitter 

fn spawn_status_emitter(app: AppHandle, session_id: u64)

Spawn the 500 ms event-push thread. Loops emitting recording-status until the session is gone from RecordingState. Self-terminates on session end so callers don’t need to track the JoinHandle. Plain std::thread rather than a tokio task — Tauri’s Emitter is sync-friendly and avoids adding a direct tokio dep (Tauri uses tokio internally but doesn’t re-export tokio::time::interval).