A Queens resident was arrested today in connection with the killing of his neighbor who had tried unsuccessfully to help him find employment. The victim, Qian Wu, 46, ran an employment agency with her husband, and was found stabbed to death Tuesday in her apartment on 40th Road in Flushing, after a neighbor reported that blood had flowed under her door into the hallway. She had sought nine orders of protection against Huang Chen, 47, the most recent one filed last Friday. (Chen had previously served 30 days in prison in 2006 for assaulting the woman.) Police found him at New York Hospital Queens with blood on his shoes, and otherwise clean clothing. They questioned him, and later spotted him on a security tape leaving the apartment building soon after the crime with a bag. When they recovered the bag from a nearby park, it contained a knife, hammer and bloody clothes.