s apply federal law to resolve work-product privilege y claims and state law to resolve alto ey-cli- ent privilege claims."); Maertin . Arm- strong World Industries, Inc., 17 F.R.D. 143, 147 (D.N.J.1997) ("[T]he work product privilege is governed, even in di- versity cases, by iform federal law..."); S.D. Warren Co