fix: reconcile instance status with Docker on list, add IsContainerRunning

internal/api/instances.go

@@ -33,6 +33,27 @@ func (s *Server) listInstances(w http.ResponseWriter, r *http.Request) {
 		respondError(w, http.StatusInternalServerError, "internal server error")
 		return
 	}
+
+	// Reconcile instance statuses with Docker's actual state.
+	ctx := r.Context()
+	for i, inst := range instances {
+		if inst.ContainerID == "" || inst.Status == "removing" {
+			continue
+		}
+		running, err := s.docker.IsContainerRunning(ctx, inst.ContainerID)
+		if err != nil {
+			continue // Docker unreachable, keep stored status.
+		}
+		actualStatus := "stopped"
+		if running {
+			actualStatus = "running"
+		}
+		if inst.Status != actualStatus {
+			instances[i].Status = actualStatus
+			_ = s.store.UpdateInstanceStatus(inst.ID, actualStatus)
+		}
+	}
+
 	respondJSON(w, http.StatusOK, instances)
 }