v0.22.1 — the registry check had never run

Fixed

• The registry check died of an IndentationError on the first tag after
  it was "fixed". 0.21.2's fix corrected the logic (read the isLatest
  entry) and verified it by hand; the inline python3 -c body that wrapped
  it was indented to match the surrounding YAML, Python received that
  indentation intact, and the step had never executed once. The report job
  did its job and opened #22 — the first time that surface has ever fired
  for real. The check now lives in .github/scripts/registry_latest.py
  (linted, unit-tested in tests/test_registry_latest.py, and the step body
  was run end to end locally against the live registry before tagging), and
  a new workflow-scripts step compiles every inline python -c block in
  every workflow — control-tested red against the broken form.