By Hyunjoo Jin (Reuters) -Elon Musk emailed Twitter staff on Friday asking that any employees who write software code report to the 10th floor of the office in San Francisco early afternoon, according to an email reviewed by Reuters. The billionaire said in a follow-up email, “If possible, I would appreciate it if you could fly to SF to be present in person,” adding he would be at the company’s headquarters until midnight and would return Saturday morning. He said the engineers should report at 2 p.m. on Friday. The emails came a day after hundreds of Twitter employees were estimated to have d…