v4.10.0-rc.1 — alef-backed publish pipeline (RC1)

First release candidate for v4.10.0.

This RC fires the publish workflow end-to-end against real registry endpoints with prerelease dist-tags (npm next, gem .pre.rc, PyPI rc{N}). The point is to validate the alef-backed publish refactor: each language target's publish job either lands the prerelease or surfaces a failure that we'll fix in rc.2.

See CHANGELOG.md for the full list of functional changes since v4.9.5.