chore: remove obsolete manual-publish paths (release.sh, /publish skill)

Releases now go through .github/workflows/release.yml, which builds the bundles
and publishes the npm thin-installer. The old manual paths published the root
(non-bundled) package, which would break Node < 22.5 users — remove them so they
can't be run by accident. CLAUDE.md + add-lang updated to point at the workflow.
scripts/extract-release-notes.mjs is kept (the workflow uses it).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>