Handoff

A throwaway checkpoint carrying what lives only in the conversation — the goal,
the decisions and why, the dead-ends, the exact next step — so a fresh session
resumes without re-deriving it. Out of the workspace, so nothing to maintain and
nothing to drift; it lives in temp, and a reboot wiping it is fine.

Write

• In the OS temp dir, under a per-project name so the next session finds it
  with no prompting: $TMPDIR/handoff/<slug>-<id>.md, where <slug> is the
  git-root path slugified and <id> is 6 characters from a UUID. Each handoff is
  its own file; print the path when done.
• Reference artifacts by path/URL, never copy — plans, ADRs, specs, commits,
  diffs. Derivable state (versions, counts, branch status) gets the command to
  derive it, not a transcribed value that rots.
• Redact secrets — keys, passwords, tokens, PII.

Include: a conversational summary (what this is, where it stands), the next
step and how to pick it up, suggested skills for the continuation, and — if
an argument is given — shape the handoff toward that focus.

Resume

In a new session, when the user asks to resume, glob $TMPDIR/handoff/<slug>-*.md
for this repo's slug and read the newest. If none exists, say so.