An 8-year-old girl is evaluated for persistent difficulty concentrating in school and at home. Her parents report she has always been 'daydreamy' and forgetful, losing belongings frequently and forgetting instructions. She does not fidget excessively or interrupt others. Classroom observations confirm poor sustained attention during independent work but no hyperactivity. Her teacher notes she performs better in one-on-one settings. Neuropsychological testing reveals average intelligence with relative weakness in working memory and processing speed. What is the MOST likely ADHD presentation in this child?