Write or update a handoff document so the next agent with fresh context can continue.

Steps

If HANDOFF.md exists in the project root, read it first.
Do not duplicate content already in PRDs, plans, ADRs, issues, commits, or diffs — reference them by path or URL.
Write or update HANDOFF.md in the project root with:
- Goal — what we're trying to accomplish
- Current Progress — what's done (link commits/PRs)
- In flight — running or cut work, if any: run id and resume command, branch or worktree, uncommitted paths and their owner, submitted remote jobs
- What Worked — approaches that succeeded
- What Didn't Work — dead ends, so they aren't retried
- Next Steps — concrete action items
- Suggested skills — which skills the next session should load, if any
If the user passed arguments, tailor the doc to that focus.
Tell the user the path so they can start a fresh conversation with it.