trackTimestamp method
Record a timestamp for an event name.
Implementation
void trackTimestamp(String eventName, int tsMillis) {
// Remove first so re-insertion moves to end (most recent)
_timestamps.remove(eventName);
if (_timestamps.length >= _maxEntries) {
// Evict oldest inserted entry (first key in insertion order)
_timestamps.remove(_timestamps.keys.first);
}
_timestamps[eventName] = tsMillis;
}