cendor-sdk 1.0.1

Changed

• Packaging & docs only — no code changes. Split the README into a repo landing (README.md)
  and a clean PyPI project description (README-pypi.md, now the [project.readme]), so the PyPI
  page is a self-contained product description with working links. Removed references to the
  internal plan/ design docs from the shipped README / docs / CHANGELOG, and untracked plan/
  (kept local, gitignored) so it never ships. The cendor.sdk package code is identical to 1.0.0.