Produces a complete, executable plan for restructuring a codebase from a monolithic layer-by-type layout (flat components/, hooks/, services/, utils/...) into feature-driven architecture (features/<feature>/ + shared/). Use when the user wants to refactor, restructure, or migrate an app from monolith to feature-based/feature-driven/vertical-slice architecture, or asks to "analyze the structure for refactoring". The output is a written plan; execution only starts after the user approves it.
