Intent

Introduce a Better Harness checkpoint as a sealed, local state anchor for one completed Harness artifact run. Later analysis can list, inspect, validate, and selectively load allowlisted prior context without changing project files, restoring an agent transcript, switching a Git branch, or claiming that old artifact bytes have been retained.

The design adopts Entire CLI's separation between a lightweight checkpoint summary and checkpoint content, but rejects Entire's code-state and Git-history semantics. In Better Harness, a checkpoint is a run continuity index, not a source-code rollback mechanism.