Persist current world history

internal/app/world_history.go

@@ -25,6 +25,7 @@ type WorldVisit struct {
 type worldHistorySnapshot struct {
 	UpdatedAt time.Time    `json:"updated_at"`
 	Visits    []WorldVisit `json:"visits"`
+	Current   *WorldVisit  `json:"current,omitempty"`
 }
 
 type WorldHistoryTracker struct {
@@ -61,6 +62,10 @@ func (t *WorldHistoryTracker) load() error {
 		return err
 	}
 	t.visits = mergeWorldVisits(snap.Visits)
+	if snap.Current != nil && !snap.Current.StartedAt.IsZero() {
+		current := *snap.Current
+		t.current = &current
+	}
 	return nil
 }
 
@@ -188,6 +193,7 @@ func (t *WorldHistoryTracker) persistLocked() error {
 	return enc.Encode(worldHistorySnapshot{
 		UpdatedAt: time.Now(),
 		Visits:    mergeWorldVisits(t.visits),
+		Current:   t.current,
 	})
 }