Agent Skills: handoff-memory

Create, refresh, validate, and resume shared HANDOFF and memory documents for a repository, a workspace-wide cross-repo context, or a workstream inside a larger workspace. Use when asked to write a handoff, checkpoint progress, resume prior work, or standardize project-state notes in Git-trackable files such as `docs/HANDOFF.md`, `_memory/HANDOFF.md`, or `_memory/workstreams/checkout-flow/HANDOFF.md`.