feat(npm): mkS390xNpmPublishMulti — multi-version npm publish per tag (#192)

Mirrors mkPyPiWheelPublishMulti for npm: publishes a fixed {version,file,
distTag?} list, each staged into its own dir and npm-published with its
dist-tag (idempotent). file may be a .node or a plain binary; packageJson
declares main-vs-bin. Unblocks nextjs-swc (next15 dist-tag) + sentry-cli.
Shared parity_npm_publish_dir helper added.

CHANGELOG.md

@@ -7,6 +7,15 @@ semantic versioning; the version is a conceptual tag (no git tag is created).
 
 ## Unreleased
 
+- **Feature: `mkS390xNpmPublishMulti` (cluster #192).** A multi-version npm
+  builder mirroring the PyPI multi one: publishes a fixed list of
+  `{ version; file; distTag? }` per tag, each staged into its own dir and
+  `npm publish`ed with its dist-tag (idempotent — "already exists" == success).
+  `file` may be a `.node` addon OR a plain binary, and `packageJson` (with a
+  `$VERSION` the stage heredoc expands) declares the shape (`main` vs `bin`), so
+  it covers both nextjs-swc (16.1.6 `@latest` + 15.2.0 `@next15`) and sentry-cli
+  (a binary published as an npm package at two versions). Shared
+  `parity_npm_publish_dir` helper added to `ci/parity-lib.sh`.
 - **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.