fix(orchestrator): prevent concurrent double-run duplicating messages; reflect errors in status

internal/httpapi/run.go

@@ -74,6 +74,10 @@ func (s *Server) handleRun(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "accounts must pass connection tests first", http.StatusConflict)
 		return
 	}
+	if errors.Is(err, orchestrator.ErrAlreadyRunning) {
+		http.Error(w, "task is already running", http.StatusConflict)
+		return
+	}
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return