feat(pypi): mkPyPiWheelPublishMulti — publish all versions per tag (#197)

Single-version mkPyPiWheelPublish made consumers ship only the default
version per tag. Add a multi-version builder that loops over a fixed
{version,wheel} list (version parsed from the wheel filename, idempotent
409-skip), plus shared parity_pypi_post/parity_wheel_version helpers.

CHANGELOG.md

@@ -7,6 +7,13 @@ semantic versioning; the version is a conceptual tag (no git tag is created).
 
 ## Unreleased
 
+- **Feature: `mkPyPiWheelPublishMulti` (cluster #197).** A multi-version PyPI
+  builder that publishes a fixed list of `{ version; wheel; }` per tag instead of
+  just the default — the pre-parity behaviour several `*-s390x` repos rely on.
+  Each wheel's real version is read from its filename (PEP 427), so
+  stage/publish/push-staged need no side-channel map and a re-run is idempotent
+  (409-skip per version). Shared `parity_pypi_post` / `parity_wheel_version`
+  helpers added to `ci/parity-lib.sh`. First consumer: `numpy-s390x` (5 versions).
 - **Fix (safety): dev-tag guard was ineffective.** Every publish app body runs
   `VERSION="$(parity_derive_version <default>)"` before `parity_devtag_guard`, so
   by the time the guard checked `$VERSION` it was always non-empty (the derived