Canonical docs:
docs/ARCHITECTURE.mddocs/CONTRACT.md
Execution plans:
docs/workplan/PRE_SPRINT.mddocs/workplan/PLAN_BACKEND_PHASE1.mddocs/workplan/PLAN_FRONTEND_PHASE1.mddocs/workplan/PLAN_BACKEND_PHASE2.mddocs/workplan/PLAN_FRONTEND_PHASE2.md
Read docs/ARCHITECTURE.md for the repo boundary, then use the relevant
docs/workplan/ document for execution.