The company doing the first government-approved test of embryonic stem cell therapy is discontinuing further stem cell work, a move with stark implications for a field offering hope of future medicines for conditions with inadequate or no current treatments. Geron Corp., a pioneer in stem cell research that has been testing a spinal cord injury treatment, said late Monday that it’s halting development of its stem cell programs to conserve funds. It is seeking partners to take on the programs’ assets and is laying off much of its staff.