<Purpose Deep Dive orchestrates a 2-stage pipeline that first investigates WHY something happened (trace) then precisely defines WHAT to do about it (deep-interview). The trace stage runs 3 parallel causal investigation lanes, and its findings feed into the interview stage via a 3-point injection mechanism — enriching the starting point, providing system context, and seeding initial questions. The result is a runtime-portable spec grounded in evidence, not assumptions. </Purpose <Use When - User has a problem but doesn't know the root cause — needs investigation before requirements - User say…