A 36-year-old male software engineer is referred by his primary care provider for 'anxiety.' He reports difficulty concentrating at work, restlessness during meetings, and a sense of being overwhelmed by his task list. On closer interview, he reveals that he has always had trouble finishing projects, frequently loses his keys and wallet, and was known as the 'smart kid who never turned in homework' throughout school. He describes his mind as 'always going' but clarifies it is not worry — rather, he jumps rapidly from one thought or idea to another. He denies excessive worry about health, finances, or relationships. He sleeps well when he finally gets to bed but often stays up late because he loses track of time. His PHQ-9 is 4 and GAD-7 is 6. Which diagnosis best explains his presentation?