Why: establish the authorized task workspace and its initial baseline.
Evidence: preserved precheck receipt in .task/feature-g1-ext-b1-b3.md; R0=2e92b184f3f257bbe9c90fd9e8278c2b6f192251.
Impact: task metadata only; the feature workspace starts at 2e92b184f3.
Refs: .task/feature-g1-ext-b1-b3.md