After multiple restructurings and selling off its iconic U District office tower, Safeco Insurance has allowed itself to be eaten by Liberty Mutual. Now there’ll be one fewer corporate board to hit up for charitable donations, one fewer set of bigwigs to serve on blue-ribbon civic improvement task forces. And they’re not yet talking about how many head-office troops will be fired. But the Safeco brand will remain, which means the signs on Safeco Field stay up, at least for now.