0.20.1

• Track Worktree 0.9.0. worktree:managing-worktrees ends work with
  worktree finish --discard-cache --archive <tree>: it deletes only ignored build cache the CLI
  recognises by structure, archives everything else no remote ref recovers, and finishes. The skill
  no longer asks agents to prove they own a build directory before deleting it, which left 105
  trees (49.0 GB) unfinished on one machine, and it forbids deleting a build directory by name,
  because agents write records into target/.
• A sub-agent that creates a tree finishes it before it returns or returns its id and path; the
  parent finishes every returned tree. In 14 days of transcripts, 105 of 153 sub-agent sessions
  created a tree and never finished it.
• AEP wave teardown uses the same command: unpublished wave commits go into a local archive instead
  of keeping the tree, and only scratch outside the tree is removed by exact path.
• The governed-plan tutorial and the Worktree plugin page describe the new finish.