Method attach

include/workspace/workspace.hpp:109–114

* @brief attach a workbranch * @param br ptr (heap memory) * @return id * @note O(1) */

     * @note O(1)
     */
    bid attach(workbranch* br) {
        assert(br != nullptr);
        branches.emplace_back(br);
        cur = branches.begin();  // reset cursor
        return bid(br);
    }
    /**
     * @brief attach a supervisor
     * @param sp ptr (heap memory)