Draft or complete technical plans before implementation. Use when a user asks Codex to write, create, draft, fill in, complete, refine, or update a technical design, detailed implementation plan, ADR, feature design, architecture proposal, API/data-model proposal, migration plan, or design document. Produces or updates per-feature requirements, design, and implementation-plan documents with data structures, changed fields, data flow, object lifecycle, diagrams, risks, tests, rollout, and a writer-scoped git commit when safe. Does not approve or reject the plan.
