By Steve Gorman and Helen Coster (Reuters) -Unionized journalists at The Washington Post said they would stage a 24-hour strike on Thursday to protest staff cuts and what they call management’s failure to bargain in good faith in contract talks that have stretched on for 18 months. The planned one-day walkout would mark the first general work stoppage at the Post since the bitter, 20-week pressmen’s strike of 1975-76, when Katharine Graham was publisher, according to union officials. The latest labor clash comes a little more than a month after William Lewis, former publisher of The Wall Stree…