Backlog Charter

Create and amend CHARTER.md, the opt-in project reference axis used to measure backlog work, sprint plans, and drift. This skill is rerunnable and routes on file state: no repo-root CHARTER.md means create mode; an existing repo-root CHARTER.md means amend mode.

What CHARTER.md Is

CHARTER.md lives at the target repo root as a peer of README.md. It records what good looks like: the problem, approach, explicit non-goals, verifiable objectives, and immutable decision history the backlog is measured against.

Absence is supported. Projects opt in by creating the file; other skills degrade gracefully when it is missing. Keep the charter under a ~5-minute read. Operational know-how does not belong here; put rediscovery-prone HOW-knowledge in _context.md.

3 Tiers