Phase 2 of the case-writer pipeline. Lock structural decisions for a Harvard-style MBA teaching case — case type, protagonist, ending mode (A Pure Interrupted / B Implied Tension / C Narrative Deliberation / D Structured Fork), temporal-freeze style, options, exhibits, learning objectives, difficulty calibration. Ends with a HARD user-approval gate (QG1) that advances spec status from DRAFT to APPROVED. Use after `case-writer-research` produces a DRAFT spec.
