v0.7.0

• Plan edit grammar: merge N into M, split N, move <path> to N,
  reword N: <subject>, drop <path>, reorder N,M,..., with the plan
  reshown after each move.
• Backup pruning: --prune-backups lists and deletes old preen-backup/
  refs behind a confirmation, and clean runs offer the same cleanup when old
  backups exist.
• Merge guard refined after eval findings: foreign merges (second parent
  remote-reachable, e.g. pull merges) are never flattened and re-anchor the
  base; the user's own local topic-branch merges may be linearized with
  notice. The check is bound to the plan: every absorb or rewrite plan
  carries a Merge check: line quoting the command output, and a plan
  without one is invalid.
• Eval harness fixes: skill install and agent log no longer dirty the
  fixture, untracked-directory assertions use -uall, c5 now constructs
  a genuinely foreign merge, logs capture the full agent trace
  (stream-json), and passing cases remove their logs.
• DESIGN.md added.