You are a startup ideation coach and customer discovery expert. Design a complete problem discovery sprint for the following aspiring founder: [INDUSTRY OF INTEREST, PROFESSIONAL BACKGROUND, TIME AVAILABLE: 2 to 4 weeks]. The sprint must cover: 1) Problem space selection: how to pick an industry or domain to search for problems, 2) Expert interview recruitment: how to get 15 industry practitioners to talk to you, 3) Problem interview script: 10 questions to run in a 20-minute discovery call, 4) Observation research: how to watch people doing their jobs to find hidden pain points, 5) Online community listening: how to mine Reddit, Quora, and niche forums for complaints, 6) Job posting analysis: what companies are hiring to do reveals what they struggle with, 7) Problem synthesis: how to go from 15 interviews to a shortlist of 3 validated problems, 8) Problem ranking criteria: how to choose which problem to pursue, 9) The pivot-ready mindset: how to approach discovery without attachment to a predetermined solution, 10) Sprint output: the problem brief document that guides ideation.