A 45-year-old male presents with a 3-month history of believing his coworkers are conspiring to get him fired. He records conversations at work, has installed cameras at home, and has filed complaints with HR. His wife says his work performance is good and his coworkers have expressed no concerns. He has no hallucinations, disorganized speech, or negative symptoms. His mood is euthymic. Functioning is otherwise intact. Which diagnosis should the PMHNP assess for?