chore(release): v0.2.1 (#20)

[0.2.1] — 2026-09-23

• perf(yaml): the billion-laughs pre-scan only runs on documents that
  contain anchors (&); alias-free configs keep the old 2.2 ms/100 KB.
• feat(release): the bump commit now carries its own CHANGELOG section and
  GitHub-release notes; a CI tripwire fails if CHANGELOG and Cargo.toml drift.
• fix(release): compute the next version from the semver-max of remote tags
  (git describe is blind to the orphaned 0.2.0 bump); tag v0.1.1 — a bogus
  patch produced by that blindness — was withdrawn from tags and releases.
• fix(ci): restore the v0.2.0 version bump that the release flow never pushed
  (the workflow guard swallowed every bump push to protected main).
• docs: benchmark tables and charts regenerated for the lossless-Node
  emitters (JSONC/TOML/YAML/INI dumps ~25% faster); launch posts live outside
  the site build.