The crate's implementation is M5 through M7 in the workspace
[CHECKLIST.md](../../CHECKLIST.md). Completed plans are recorded in
[COMPLETED-PLANS.md](COMPLETED-PLANS.md). Design decisions are in
[DESIGN-NOTES.md](DESIGN-NOTES.md), with rationale in
[DESIGN-RATIONALE.md](DESIGN-RATIONALE.md).