Function startPolling

frontend/src/stores/simulation.ts:270–281

* Start background polling. Safe to call multiple times — creates at most * one timer. Performs an immediate refresh before starting the interval.

(interval?: number)

   * one timer. Performs an immediate refresh before starting the interval.
   */
  function startPolling(interval?: number): void {
    if (pollingTimer !== null) return; // already polling
    if (interval !== undefined) {
      pollInterval.value = interval;
    }
    void refreshAll();
    pollingTimer = window.setInterval(() => {
      void refreshAll();
      // Sync the playback cursor to live time when not scrubbing.
      tickPlaybackSync();
    }, pollInterval.value);
  }

  /** Stop background polling and clear the timer. */
  function stopPolling(): void {