“San Francisco” is a halting snapshot of a singular talent. London-based Laurel Arnell-Cullen is able to sound wounded while rising up from her troubles (here, a lover heading across the Atlantic) while a hazy mist of soulful guitars and drums circulate. It’s a heady brew and helps build upon the deafening buzz created by formative alt-pop standouts like the self-written, performed, recorded and produced “Life Worth Living”.