In a tweet, newly permanent Twitter CEO Jack Dorsey confirmed the layoff rumors at the lagging social networking company. "Made some tough but necessary decisions that enable Twitter to move with greater focus and reinvest in our growth," he wrote, linking to a company-wide email announcing the cuts. The email, with the subject line 'A more focused Twitter', said that up to 336 jobs — 8 percent of its workforce — could be cut company-wide, with particular emphasis on the product and engineering…