A 24-year-old female college student presents with a 2-year history of excessive daytime sleepiness that has progressively worsened despite adequate nighttime sleep of 8-9 hours. She reports sudden episodes of bilateral knee buckling and jaw slackening triggered by laughter or surprise, lasting 10-30 seconds during which she remains fully conscious. She also describes vivid, frightening hallucinations occurring at sleep onset and occasional episodes of being unable to move for 1-2 minutes upon awakening. Her polysomnography shows a sleep latency of 3 minutes with sleep-onset REM period, and subsequent multiple sleep latency test (MSLT) reveals a mean sleep latency of 4.2 minutes with 3 sleep-onset REM periods (SOREMPs) out of 5 naps. Which of the following is the most likely diagnosis?