Modernize release workflow and populate release description from tag annotation

Replace deprecated actions/create-release and actions/upload-release-asset
with a single gh release create call that uploads assets as positional
arguments and uses --notes-from-tag to pull the annotated tag message as
the release body. Also updates checkout and setup-node to v4 and bumps
Node to 20.x.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>