v0.4.4 — self-update command, apply-zip structure fixes, backups removed

Added

• contextzip update / cz update — checks PyPI for a newer release and
  updates in place, matching however you installed it (pip, pipx, or
  uv tool). --check to just see if one's available, --yes to skip
  the confirm.
• .contextzip/inbox/ now comes with a README.txt, created the moment
  the workspace is first set up, explaining what the folder is for and
  how to use it.

Fixed

• apply-zip was dumping a zip's wrapper folder verbatim (e.g.
  project/app/dashboard/... instead of app/dashboard/...) in two
  related cases: when the wrapper's name happened to match a real folder
  already in the project, and when the manifest used to check was scoped
  to a small subset of the project (e.g. a git-diff manifest) and
  couldn't settle the decision either way. Both now resolve correctly —
  the first via manifest match-rate comparison, the second via a
  fallback to the project's real on-disk directory layout.
• apply-zip <path> was writing its .apply-report.txt next to the
  zip's own location — so pointing it at a zip outside
  .contextzip/inbox/ (e.g. one sitting in your project root) left a
  stray report cluttering the repo. Reports now always go to
  .contextzip/inbox/.
• Auto-cleanup wasn't pruning old apply-report.txt files left loose in
  .contextzip/inbox/ — they now get cleaned up like everything else.

Removed

• The .contextzip/backups/ per-apply backup mechanism, entirely.
  apply-zip no longer backs up overwritten files before writing them;
  the manifest-diff confirmation and the always-archived applied zip
  remain the safety net. Any leftover backups/ folder from an older
  install is now wiped outright by auto-cleanup.

Full Changelog: v0.4.2...v0.4.4